SOLUTION: Do I use the standard form or the vertex form for a parabola to solve the following equation on a graph? f(x)=x^2-7x-8 (I need to know what the vertex, line of symmetry, x-i

Algebra ->  Quadratic-relations-and-conic-sections -> SOLUTION: Do I use the standard form or the vertex form for a parabola to solve the following equation on a graph? f(x)=x^2-7x-8 (I need to know what the vertex, line of symmetry, x-i      Log On


   

Question 317033: Do I use the standard form or the vertex form for a parabola to solve the following equation on a graph?
f(x)=x^2-7x-8
(I need to know what the vertex, line of symmetry, x-intercepts, and opening of the graph are)
Thanx!! =)





Answer by Fombitz(32388) About Me  (Show Source):
You can put this solution on YOUR website!
Vertex form. Complete the square to get there.
f%28x%29=x%5E2-7x-8
f%28x%29=x%5E2-7x%2B49%2F4-8-49%2F4
f%28x%29=%28x-7%2F2%29%5E2-32%2F4-49%2F4
f%28x%29=%28x-7%2F2%29%5E2-81%2F4
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.
Vertex is (7%2F2,-81%2F4).
Axis of symmetry is x=7%2F2
Coefficient of x%5E2 term is positive, parabola opens upwards.
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Solve to get the x-intercepts,
f%28x%29=%28x-7%2F2%29%5E2-81%2F4=0
%28x-7%2F2%29%5E2=81%2F4
x-7%2F2=0+%2B-+9%2F2
x=7%2F2+%2B-+9%2F2
x=8 and x=-1
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