SOLUTION: For the problem f(x)=×2+2x-15, I need to find the vertex, the x and y intercepts, axis of symmetry, and the concavity. If you could show how you got your answers so I can try to

Algebra ->  Quadratic Equations and Parabolas  -> Quadratic Equations Lessons -> SOLUTION: For the problem f(x)=×2+2x-15, I need to find the vertex, the x and y intercepts, axis of symmetry, and the concavity. If you could show how you got your answers so I can try to       Log On


   

Question 999447: For the problem f(x)=×2+2x-15, I need to find the vertex, the x and y intercepts, axis of symmetry, and the concavity.
If you could show how you got your answers so I can try to solve it and get the right answer, that would be awesome. I need to understand HOW to do the problwm so I can solve all the other questions on my homework.
Answer by Fombitz(32388) About Me  (Show Source):
You can put this solution on YOUR website!
You need to complete the square to put the equation in vertex form.
If you're unsure how to do this, search on "completing the square" on YouTube.
f%28x%29=x%5E2%2B2x-15
f%28x%29=%28x%5E2%2B2x%2B1%29-1-15
f%28x%29=%28x%2B1%29%5E2-16
So the vertex is (-1,-16).
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The vertex lies on the axis of symmetry x=-1.
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For the x-intercepts,
0=%28x%2B1%29%5E2-16
%28x%2B1%29%5E2=16
x%2B1=0+%2B-+4
x=-1+%2B-+4
x=3 and x=-5
(3,0) and (-5,0)
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For the y-intercept,
y=%280%2B1%29%5E2-16
y=1-16
y=-15
(0,-15)
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