SOLUTION: How would you write f(x)=5x^2+15x-9 in vertex form?

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Question 409868: How would you write f(x)=5x^2+15x-9 in vertex form?
Answer by edjones(8007) About Me  (Show Source):
You can put this solution on YOUR website!
a(x-h)^2+k Vertex form.
f(x)=5x^2+15x-9
=5(x^2+3x)-9
=5(x^2+3x + 9/4 - 9/4) -9
=5(x^2+3x + 9/4)-5(9/4)-9
=5(x + 3/2)^2 - 81/4 So h=-3/2, k=-81/4, a=5 the vertex is (-3/2, -81/4)
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Ed