（x-3)^2+4x(x-3)=0(x-3)(x-3+4x)=0(x-3)(5x-3)=0x-3=0x=35x-3=0x=3/5
x1=3，x2=-1
x^2-6x+9+4x^2-12x=05x^2-18x+9=0(x-3)(5x-3)=0解得x=3或者x=3/5
