SOLUTION: Use the function y=a(x+3)(2x+18). What are the x-intercepts of the function's graph? What are the coordinates of the graph's vertex?

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Question 595761: Use the function y=a(x+3)(2x+18). What are the x-intercepts of the function's graph? What are the coordinates of the graph's vertex?
Answer by lwsshak3(11628) About Me  (Show Source):
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Use the function y=a(x+3)(2x+18). What are the x-intercepts of the function's graph? What are the coordinates of the graph's vertex?
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y=a(x+3)(2x+18)
distribute
y=a(2x^2+24x+54)
y=a(x^2+12x+27)
y=a(x+3)(x+9)
solve for x-intercepts
set y=0
x+3=0
x=-3
and
x+9=0
x=-9
..
x-intercepts: -3 and -9
..
Finding coordinates of vertex
y=a(x^2+12x+27)
complete the square (assume a=1)
y=(x^2+12x+36)+27-36
y=(x+6)^2-9
Vertex:(-6,-9)