Hi,  

the vertex form of a parabola,  where(h,k) is the vertex

vertex (-5,80)

y =a(x+5)^2 + 80

using y-intercept pt(0,45) to find a

45 = a(5)^2 + 80

-35 = a*25

 -35/25 = a

y = -7/5(x+5)^2 +80  OR y = -7/5[x^2 +10x + 25] + 80

finding x-intercepts  (y = 0)

-7/5[x^2 +10x + 25] + 80 = 0

 -7/5x^2 - 14x -35 + 80 = 0

 -7/5x^2 - 14x +45 = 0





 

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