Question 440161
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Hi
Using the vertex form of a parabola, {{{y=a(x-h)^2 +k}}} where(h,k) is the vertex
vertex (0, 18) 
 y = ax^2 + 18      |passing through (-3, 0) 
 0 = a*9 + 18
-18 = 9a
-2 = a
 y = -2x^2 + 18

Write the quadratic function in the vertex form. 
y = -3x^2 - 30x - 71    |Completing the square to do so
y = -3[x^2 +10x] - 71 
y = -3[(x+5)^2 -25] - 71
y = -3(x+5)^2 + 75 - 71
y = -3(x+5)^2 + 4