Question 869742
Y=-5x^2+30x-36

Y=-5(x^2-6x)-36


Recall (a-b)^2=a^2-2ab+b^2

we have a^2-2ab

which is
x^2-(2)(3)x

adding 9 will make it a perfect square

x^2-(2)(3)(3)+9

we have added 9 so we have to subtract 9

x^2-6x+9-9

Finally we have
y= -5(x^2-6x+9-9) -36

y=-5((x-3)^2-9)-6^2