What is the axis of symmetry for f(x) = 2x2 + 8x + 8?

Question

antonio_xx2 · Answer

http://www.wolframalpha.com/input/?i=axis+of+symmetry+for+f%28x%29+%3D+2x^2+%2B+8x+%2B+8+ \ from the sketch it looks like x=-2 ;)

aaronq · Answer

If you want the answer analytically, then take the first derivative, set it to zero and find the solution(s).

 $\sf f(x) = 2x^2 + 8x + 8$

 $\sf f('x) = 4x + 8=0\rightarrow x=\dfrac{-8}{4}=-2$

This gives you the x coordinate of the point on the parabola where a tangent to it has the slope =0. This is where the vertex is and where it would divide the parabola in half (vertically).

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