移项ax+by=cby=-ax+c两边除以by=-(a/b)x+c/b
3a-2=1-a3a+a=1+24a=3a=3÷4a=3/44x(2x2-x+1)+2(2x-1)-4(1-2x2)=8x3-4x2+4x+4x-2-4+8x2=8x3+4x2+8x-6=8×1+4×1+8×1-6=14
