Answer:
y = 15(x -10)^2 -1560
Step-by-step explanation:
It usually works well to divide the leading coefficient from the x terms:
y = 15(x^2 -20x) -60
Now, add the square of half the x-coefficient inside parentheses. Subtract the same amount outside.
y = 15(x^2 -20x +100) -60 -(15)(100)
y = 15(x -10)^2 -1560 . . . . . collect terms; write the parentheses as a square
