SOLUTION: Select the x-coordinate of the vertex of the parabola defined by the function f(x)=-9x^2+7x+8

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Question 884910: Select the x-coordinate of the vertex of the parabola defined by the function f(x)=-9x^2+7x+8
Found 2 solutions by josgarithmetic, MathTherapy:
Answer by josgarithmetic(39617) About Me  (Show Source):
You can put this solution on YOUR website!
Complete the Square to put the function into standard form and then read the x value for vertex from the function.

f%28x%29=-9%28x%5E2-%287%2F9%29x%29%2B8
-9%28x%5E2-%287%2F9%29x%2B%287%2F%282%2A9%29%29%5E2%29%2B8%2B9%287%2F%282%2A9%29%29%5E2
-9%28x-7%2F18%29%5E2%2B8%2B9%287%2F%282%2A9%29%29%5E2

Although the arithmetic simplifying the constant term is not finished, the x value for the vertex is highlight%28x=7%2F18%29.

Also study this lesson:
Also shows standard form: Completing the Square to Solve General Quadratic Equation

Answer by MathTherapy(10552) About Me  (Show Source):
You can put this solution on YOUR website!
Select the x-coordinate of the vertex of the parabola defined by the function f(x)=-9x^2+7x+8


x-coordinate of the vertex is: h+=+-+b%2F2a, with: a being - 9, and b being 7

h+=+-+b%2F2a becomes h+=+-+7%2F%282%28-+9%29%29

x-coordinate of vertex: highlight_green%28highlight_green%28h+=+7%2F18%29%29