Graph of Quadratic Function/Solving Quadratic Equation for (a=2,b=-13,c=-10)

Let us consider the following quadratic function: f(x) = 2x2 -13x -10

The solutions of the quadratic equation 2x2 -13x -10 = 0 correspond to the zeros or the roots of the function f(x) = 2x2 -13x -10. 
These are the points where the graph of f(x) cuts the x-axis. The graph cuts the Y-axis at -10.

The Discriminant and Roots of the Quadratic Equation 2x2 -13x -10 = 0

The standard form of a quadratic equation is ax2 + bx + c = 0, where "a" does not equal 0. Note that if a = 0, the x2 term would disappear and the equation would be linear.
Looking at the given quadratic function  a = 2, b = -13, c = -10. 
The discriminant D = b2 - 4ac = -132 - 4 * (2) * (-10) = 249.0
The roots of the equation are  (-b - √D)/2a and (-b + √D)/2a 
= (-(-13) - √249.0)/(2(2)) and (-(-13) + √249.0)/(2(2))
-0.695 and 7.195 

The discriminant is positive. Hence, the roots are real and unequal. The quadratic curve cuts the X axis at two distinct points.
The value of 'x' in the intervals (x < -0.695) and (x > 7.195) satisfy the inequality 2x2 -13x -10 > 0


Graph of y = f(x) = 2x2 -13x -10
Quadratic Polynomial Parabola


Geometric and Graphical interpretation: Curve Sketching


The function f(x) = 2x2 -13x -10 is the quadratic function. The graph of any quadratic function has the same general shape. This shape is called a parabola. The location and size of the parabola, and how it opens, depend on the values of coefficients in the function. This parabola has a minima point and opens upwards. The graph of the parabola is symmetric with respect to the vertical line passing through the vertex. 

The x-coordinate of the vertex will be located at x = (-b/2a) = (-(-13))/(2*2) = 3.25, and the y-coordinate of the vertex is -31.13 which we obtain by substituting the value x = 3.25 in 2x2 -13x -10. This is the minima value attained by the quadratic function f(x). The derivative of the function is 0 at this point. This point is a turning point or a stationary point.
The solutions of the quadratic equation 2x2 -13x -10 = 0 correspond to the zeros or the roots of the function f(x) = 2x2 -13x -10.  As shown in the figure, when the coefficients a, b, and c are real numbers and the domain of f is the set of real numbers, then the roots of f are exactly the x-coordinates of the points where the graph touches the x-axis. The discriminant is positive. Hence, the roots are real and unequal. The quadratic curve cuts the X axis at two distinct points.
The value of 'x' in the intervals (x < -0.695) and (x > 7.195) satisfy the inequality 2x2 -13x -10 > 0

The vertex is the lowest point on the parabola if the parabola opens upward (coefficient a > 0) and is the highest point on the parabola if the parabola opens downward (coefficient a < 0)


Here's another quadratic curve here.
Many of these concepts are a part of the Grade 9,10,11,12 (High School) Mathematics syllabus of the UK GCSE curriculum, Common Core Standards in the US, ICSE/CBSE/SSC syllabus in Indian high schools. You may check out our free and printable worksheets for Common Core and GCSE.



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