Hi

Using the vertex form of a parabola,  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

 

 

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