x^2-9x<=0
3) -4x^5y^2×3xy^4=-12x^6y^6
(3x^2y^3)^2=9x^4y^6
y=x²+2x-8
y+?=x²+2x+?-8
y+?=x²+2x+1-8
y+1=x²+2x+1-8
y+1=(x+1)²-8
y=(x+10²-8-1
y=(x+1)²-9