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Make sure the equation is written in standard form. Identify the related function and graph it.
Solutions: - 10 and 8
Graph:
We are asked to solve the given quadratic equation. We will solve it by graphing. There are three steps to solving a quadratic equation by graphing.
Equation:& x^2 + 2x - 80 = 0 Related Function:& f(x)= x^2 + 2x - 80
To draw the graph of the related function written in standard form, we must start by identifying the values of a, b, and c. f(x)= x^2+2x-80=0 ⇕ f(x)= 1x^2+ 2x+( - 80) We can see that a= 1, b= 2, and c= - 80. Now, we will follow three steps to graph the function.
Next, we will make a table of values using x-values around the axis of symmetry x=- 1.
x | x^2+2x-80 | f(x) |
---|---|---|
- 3 | ( - 3)^2+2( - 3)-80 | - 77 |
- 2 | ( - 2)^2+2( - 2)-80 | - 80 |
- 1 | ( - 1)^2+2( - 1)-80 | - 81 |
0 | 0^2+2( 0)-80 | - 80 |
1 | 1^2+2( 1)-80 | - 77 |
We can finally draw the graph of the function. Since a=1, which is positive, the parabola will open upwards. Let's connect the points with a smooth curve.
Let's identify the x-intercepts of the graph of the related function.
We can see that the parabola intersects the x-axis twice. The points of intersection are ( - 10,0) and ( 8,0). Therefore, the equation x^2+2x-80=0 has two solutions, approximately x= - 10 and x= 8.