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Evaluating Expressions Part 1

"Evaluation of an expression" generally means "simplifying an expression down to a final numerical value". In this lesson, we'll concentrate on the "plug" aspect of evaluation: plugging in values for variables, then computing the value of an expression for a given value of the variable.

A variable is a letter, for example x, y or z, and it represents an unspecified numeric value. To evaluate an algebraic expression, you have to substitute a number for each variable and perform the arithmetic operations prescribed by the expression.
Usually the only difficult part in evaluation is in keeping track of the minus signs. It is strongly recommended to use parenthesis generously, for clarity and accuracy.
We will focus on polynomial functions in one variable, for now.

Example 1: Consider the Polynomial: -6 +8x -3x2

Evaluate the expression for x=-15, x=2, x=9, x=-4

Evaluating the given expression for x = -15
Let us compute. The required value = -6 +8*(-15) -3*(-15)2
=-801

Evaluating the given expression for x = 2
Let us compute. The required value = -6 +8*(2) -3*(2)2
=-2

Evaluating the given expression for x = 9
Let us compute. The required value = -6 +8*(9) -3*(9)2
=-177

Evaluating the given expression for x = -4
Let us compute. The required value = -6 +8*(-4) -3*(-4)2
=-86

Example 2: Consider the Polynomial: - +7x +4x2

Evaluate the expression for x=-12, x=-2, x=2, x=-20, x=1

Evaluating the given expression for x = -12
Let us compute. The required value = (-12)0 +7*(-12) +4*(-12)2
=491

Evaluating the given expression for x = -2
Let us compute. The required value = (-2)0 +7*(-2) +4*(-2)2
=1

Evaluating the given expression for x = 2
Let us compute. The required value = (2)0 +7*(2) +4*(2)2
=29

Evaluating the given expression for x = -20
Let us compute. The required value = (-20)0 +7*(-20) +4*(-20)2
=1459

Evaluating the given expression for x = 1
Let us compute. The required value = (1)0 +7*(1) +4*(1)2
=10

Example 3: Consider the Polynomial: -10 -x +3x2

Evaluate the expression for x=-2, x=-10, x=6, x=13, x=-16

Evaluating the given expression for x = -2
Let us compute. The required value = -10 (-2) +3*(-2)2
=4

Evaluating the given expression for x = -10
Let us compute. The required value = -10 (-10) +3*(-10)2
=300

Evaluating the given expression for x = 6
Let us compute. The required value = -10 (6) +3*(6)2
=92

Evaluating the given expression for x = 13
Let us compute. The required value = -10 (13) +3*(13)2
=484

Evaluating the given expression for x = -16
Let us compute. The required value = -10 (-16) +3*(-16)2
=774

Example 4: Consider the Polynomial: -2 +4x -9x2

Evaluate the expression for x=17, x=11, x=-20, x=2

Evaluating the given expression for x = 17
Let us compute. The required value = -2 +4*(17) -9*(17)2
=-2535

Evaluating the given expression for x = 11
Let us compute. The required value = -2 +4*(11) -9*(11)2
=-1047

Evaluating the given expression for x = -20
Let us compute. The required value = -2 +4*(-20) -9*(-20)2
=-3682

Evaluating the given expression for x = 2
Let us compute. The required value = -2 +4*(2) -9*(2)2
=-30

Example 5: Consider the Polynomial: -2 -5x -3x2

Evaluate the expression for x=-18, x=-14, x=-9, x=14, x=19

Evaluating the given expression for x = -18
Let us compute. The required value = -2 -5*(-18) -3*(-18)2
=-884

Evaluating the given expression for x = -14
Let us compute. The required value = -2 -5*(-14) -3*(-14)2
=-520

Evaluating the given expression for x = -9
Let us compute. The required value = -2 -5*(-9) -3*(-9)2
=-200

Evaluating the given expression for x = 14
Let us compute. The required value = -2 -5*(14) -3*(14)2
=-660

Evaluating the given expression for x = 19
Let us compute. The required value = -2 -5*(19) -3*(19)2
=-1180

Example 6: Consider the Polynomial: +7 -2x -8x2

Evaluate the expression for x=15, x=-20, x=16, x=1, x=-15

Evaluating the given expression for x = 15
Let us compute. The required value = +7 -2*(15) -8*(15)2
=-1823

Evaluating the given expression for x = -20
Let us compute. The required value = +7 -2*(-20) -8*(-20)2
=-3153

Evaluating the given expression for x = 16
Let us compute. The required value = +7 -2*(16) -8*(16)2
=-2073

Evaluating the given expression for x = 1
Let us compute. The required value = +7 -2*(1) -8*(1)2
=-3

Evaluating the given expression for x = -15
Let us compute. The required value = +7 -2*(-15) -8*(-15)2
=-1763

Example 7: Consider the Polynomial: +6 -5x

Evaluate the expression for x=-14, x=19, x=-18, x=-4

Evaluating the given expression for x = -14
Let us compute. The required value = +6 -5*(-14)
=76

Evaluating the given expression for x = 19
Let us compute. The required value = +6 -5*(19)
=-89

Evaluating the given expression for x = -18
Let us compute. The required value = +6 -5*(-18)
=96

Evaluating the given expression for x = -4
Let us compute. The required value = +6 -5*(-4)
=26

Example 8: Consider the Polynomial: -10 +7x +2x2

Evaluate the expression for x=-19, x=-1, x=-6, x=19

Evaluating the given expression for x = -19
Let us compute. The required value = -10 +7*(-19) +2*(-19)2
=579

Evaluating the given expression for x = -1
Let us compute. The required value = -10 +7*(-1) +2*(-1)2
=-15

Evaluating the given expression for x = -6
Let us compute. The required value = -10 +7*(-6) +2*(-6)2
=20

Evaluating the given expression for x = 19
Let us compute. The required value = -10 +7*(19) +2*(19)2
=845

Example 9: Consider the Polynomial: +4 +6x +9x2

Evaluate the expression for x=-13, x=-7, x=19, x=0, x=-8

Evaluating the given expression for x = -13
Let us compute. The required value = +4 +6*(-13) +9*(-13)2
=1447

Evaluating the given expression for x = -7
Let us compute. The required value = +4 +6*(-7) +9*(-7)2
=403

Evaluating the given expression for x = 19
Let us compute. The required value = +4 +6*(19) +9*(19)2
=3367

Evaluating the given expression for x = 0
Let us compute. The required value = +4 +6*(0) +9*(0)2
=4

Evaluating the given expression for x = -8
Let us compute. The required value = +4 +6*(-8) +9*(-8)2
=532

Example 10: Consider the Polynomial: +3 +7x +2x2

Evaluate the expression for x=-4, x=16, x=19, x=14

Evaluating the given expression for x = -4
Let us compute. The required value = +3 +7*(-4) +2*(-4)2
=7

Evaluating the given expression for x = 16
Let us compute. The required value = +3 +7*(16) +2*(16)2
=627

Evaluating the given expression for x = 19
Let us compute. The required value = +3 +7*(19) +2*(19)2
=858

Evaluating the given expression for x = 14
Let us compute. The required value = +3 +7*(14) +2*(14)2
=493

Example 11: Consider the Polynomial: -8 -2x -6x2

Evaluate the expression for x=-9, x=12, x=-12, x=14, x=5

Evaluating the given expression for x = -9
Let us compute. The required value = -8 -2*(-9) -6*(-9)2
=-476

Evaluating the given expression for x = 12
Let us compute. The required value = -8 -2*(12) -6*(12)2
=-896

Evaluating the given expression for x = -12
Let us compute. The required value = -8 -2*(-12) -6*(-12)2
=-848

Evaluating the given expression for x = 14
Let us compute. The required value = -8 -2*(14) -6*(14)2
=-1212

Evaluating the given expression for x = 5
Let us compute. The required value = -8 -2*(5) -6*(5)2
=-168

Example 12: Consider the Polynomial: +9 +4x +4x2

Evaluate the expression for x=-10, x=1, x=-12, x=-16, x=16

Evaluating the given expression for x = -10
Let us compute. The required value = +9 +4*(-10) +4*(-10)2
=369

Evaluating the given expression for x = 1
Let us compute. The required value = +9 +4*(1) +4*(1)2
=17

Evaluating the given expression for x = -12
Let us compute. The required value = +9 +4*(-12) +4*(-12)2
=537

Evaluating the given expression for x = -16
Let us compute. The required value = +9 +4*(-16) +4*(-16)2
=969

Evaluating the given expression for x = 16
Let us compute. The required value = +9 +4*(16) +4*(16)2
=1097

Example 13: Consider the Polynomial: +6 +7x +9x2

Evaluate the expression for x=17, x=2, x=-20, x=14, x=-5

Evaluating the given expression for x = 17
Let us compute. The required value = +6 +7*(17) +9*(17)2
=2726

Evaluating the given expression for x = 2
Let us compute. The required value = +6 +7*(2) +9*(2)2
=56

Evaluating the given expression for x = -20
Let us compute. The required value = +6 +7*(-20) +9*(-20)2
=3466

Evaluating the given expression for x = 14
Let us compute. The required value = +6 +7*(14) +9*(14)2
=1868

Evaluating the given expression for x = -5
Let us compute. The required value = +6 +7*(-5) +9*(-5)2
=196

Example 14: Consider the Polynomial: -9 -9x

Evaluate the expression for x=-15, x=8, x=-11, x=3, x=13

Evaluating the given expression for x = -15
Let us compute. The required value = -9 -9*(-15)
=126

Evaluating the given expression for x = 8
Let us compute. The required value = -9 -9*(8)
=-81

Evaluating the given expression for x = -11
Let us compute. The required value = -9 -9*(-11)
=90

Evaluating the given expression for x = 3
Let us compute. The required value = -9 -9*(3)
=-36

Evaluating the given expression for x = 13
Let us compute. The required value = -9 -9*(13)
=-126

Example 15: Consider the Polynomial: -8 +2x +2x2

Evaluate the expression for x=1, x=-19, x=-10, x=2, x=-9

Evaluating the given expression for x = 1
Let us compute. The required value = -8 +2*(1) +2*(1)2
=-4

Evaluating the given expression for x = -19
Let us compute. The required value = -8 +2*(-19) +2*(-19)2
=676

Evaluating the given expression for x = -10
Let us compute. The required value = -8 +2*(-10) +2*(-10)2
=172

Evaluating the given expression for x = 2
Let us compute. The required value = -8 +2*(2) +2*(2)2
=4

Evaluating the given expression for x = -9
Let us compute. The required value = -8 +2*(-9) +2*(-9)2
=136

Example 16: Consider the Polynomial: +6 +3x -2x2

Evaluate the expression for x=17, x=-14, x=-16, x=4

Evaluating the given expression for x = 17
Let us compute. The required value = +6 +3*(17) -2*(17)2
=-521

Evaluating the given expression for x = -14
Let us compute. The required value = +6 +3*(-14) -2*(-14)2
=-428

Evaluating the given expression for x = -16
Let us compute. The required value = +6 +3*(-16) -2*(-16)2
=-554

Evaluating the given expression for x = 4
Let us compute. The required value = +6 +3*(4) -2*(4)2
=-14

Example 17: Consider the Polynomial: -5 -x -5x2

Evaluate the expression for x=-1, x=0, x=-10, x=4, x=-16

Evaluating the given expression for x = -1
Let us compute. The required value = -5 (-1) -5*(-1)2
=-9

Evaluating the given expression for x = 0
Let us compute. The required value = -5 (0) -5*(0)2
=-5

Evaluating the given expression for x = -10
Let us compute. The required value = -5 (-10) -5*(-10)2
=-495

Evaluating the given expression for x = 4
Let us compute. The required value = -5 (4) -5*(4)2
=-89

Evaluating the given expression for x = -16
Let us compute. The required value = -5 (-16) -5*(-16)2
=-1269

Example 18: Consider the Polynomial: -9 +6x +3x2

Evaluate the expression for x=-5, x=-1, x=14

Evaluating the given expression for x = -5
Let us compute. The required value = -9 +6*(-5) +3*(-5)2
=36

Evaluating the given expression for x = -1
Let us compute. The required value = -9 +6*(-1) +3*(-1)2
=-12

Evaluating the given expression for x = 14
Let us compute. The required value = -9 +6*(14) +3*(14)2
=663

Example 19: Consider the Polynomial: -8x -7x2

Evaluate the expression for x=19, x=0, x=-3, x=8, x=-18

Evaluating the given expression for x = 19
Let us compute. The required value = (19)0 -8*(19) -7*(19)2
=-2678

Evaluating the given expression for x = 0
Let us compute. The required value = (0)0 -8*(0) -7*(0)2
=1

Evaluating the given expression for x = -3
Let us compute. The required value = (-3)0 -8*(-3) -7*(-3)2
=-38

Evaluating the given expression for x = 8
Let us compute. The required value = (8)0 -8*(8) -7*(8)2
=-511

Evaluating the given expression for x = -18
Let us compute. The required value = (-18)0 -8*(-18) -7*(-18)2
=-2123

Example 20: Consider the Polynomial: +6 -6x -6x2

Evaluate the expression for x=17, x=-20, x=-6, x=0, x=-16

Evaluating the given expression for x = 17
Let us compute. The required value = +6 -6*(17) -6*(17)2
=-1830

Evaluating the given expression for x = -20
Let us compute. The required value = +6 -6*(-20) -6*(-20)2
=-2274

Evaluating the given expression for x = -6
Let us compute. The required value = +6 -6*(-6) -6*(-6)2
=-174

Evaluating the given expression for x = 0
Let us compute. The required value = +6 -6*(0) -6*(0)2
=6

Evaluating the given expression for x = -16
Let us compute. The required value = +6 -6*(-16) -6*(-16)2
=-1434

Example 21: Consider the Polynomial: -3 +5x

Evaluate the expression for x=12, x=10, x=2, x=0, x=-7

Evaluating the given expression for x = 12
Let us compute. The required value = -3 +5*(12)
=57

Evaluating the given expression for x = 10
Let us compute. The required value = -3 +5*(10)
=47

Evaluating the given expression for x = 2
Let us compute. The required value = -3 +5*(2)
=7

Evaluating the given expression for x = 0
Let us compute. The required value = -3 +5*(0)
=-3

Evaluating the given expression for x = -7
Let us compute. The required value = -3 +5*(-7)
=-38

Example 22: Consider the Polynomial: +6 +5x +3x2

Evaluate the expression for x=12, x=19, x=14, x=18

Evaluating the given expression for x = 12
Let us compute. The required value = +6 +5*(12) +3*(12)2
=498

Evaluating the given expression for x = 19
Let us compute. The required value = +6 +5*(19) +3*(19)2
=1184

Evaluating the given expression for x = 14
Let us compute. The required value = +6 +5*(14) +3*(14)2
=664

Evaluating the given expression for x = 18
Let us compute. The required value = +6 +5*(18) +3*(18)2
=1068

Example 23: Consider the Polynomial: -6 -10x -5x2

Evaluate the expression for x=-15, x=11, x=-8, x=8, x=-13

Evaluating the given expression for x = -15
Let us compute. The required value = -6 -10*(-15) -5*(-15)2
=-981

Evaluating the given expression for x = 11
Let us compute. The required value = -6 -10*(11) -5*(11)2
=-721

Evaluating the given expression for x = -8
Let us compute. The required value = -6 -10*(-8) -5*(-8)2
=-246

Evaluating the given expression for x = 8
Let us compute. The required value = -6 -10*(8) -5*(8)2
=-406

Evaluating the given expression for x = -13
Let us compute. The required value = -6 -10*(-13) -5*(-13)2
=-721

Example 24: Consider the Polynomial: +8 +3x +5x2

Evaluate the expression for x=10, x=-18, x=-11, x=15, x=8

Evaluating the given expression for x = 10
Let us compute. The required value = +8 +3*(10) +5*(10)2
=538

Evaluating the given expression for x = -18
Let us compute. The required value = +8 +3*(-18) +5*(-18)2
=1574

Evaluating the given expression for x = -11
Let us compute. The required value = +8 +3*(-11) +5*(-11)2
=580

Evaluating the given expression for x = 15
Let us compute. The required value = +8 +3*(15) +5*(15)2
=1178

Evaluating the given expression for x = 8
Let us compute. The required value = +8 +3*(8) +5*(8)2
=352

Example 25: Consider the Polynomial: +5 +6x -4x2

Evaluate the expression for x=3, x=19, x=-16, x=18, x=-8

Evaluating the given expression for x = 3
Let us compute. The required value = +5 +6*(3) -4*(3)2
=-13

Evaluating the given expression for x = 19
Let us compute. The required value = +5 +6*(19) -4*(19)2
=-1325

Evaluating the given expression for x = -16
Let us compute. The required value = +5 +6*(-16) -4*(-16)2
=-1115

Evaluating the given expression for x = 18
Let us compute. The required value = +5 +6*(18) -4*(18)2
=-1183

Evaluating the given expression for x = -8
Let us compute. The required value = +5 +6*(-8) -4*(-8)2
=-299