x²-8x-84=0(x-14)(x+6)=0x=14 或x=-63分之2y的平方+3分之1y-2=02y²+y-6=0(2y-3)(y+2)=0y=3/2或y=-2
x²-8x+16=84+16（x-4)²=100x-4=±10∴x1=14，x2=-6
