2sinLcosL/cosL-sinL=sinL
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