Question 519109
this ain't rocket science ___ make the equation look like the general form


separate the constant term ___ f(x) = -4x^2 + 40x .... -13


factor ___ f(x) = -4(x^2 + 10) .... -13 ____ starting to look like something?


now the "tricky" part - complete the square ___ f(x) = -4(x^2 + 10x + 25) + 100 .... -13
___ you complete the square by taking half of the x-term coefficient, squaring it and adding it
___ the "trick" is that the square you are completing is being multiplied by a value (-4)
___ to avoid changing the overall value of f(x), you have to balance the extra -100 (the -4 times 25) by adding 100


writing in vertex form ___ -4 (x + 5)^2 + 87