(3x)^2+(4x)^2=(6-3x-4x)^2
9x^2+16x^2=(6-7x)^2
(7x-6)^2-25x^2=0
(7x-6+5x)(7x-6-5x)=0
(12x-6)(2x-6)=0
12(2x-1)(x-3)=0
x1=1/2 x2=3倒数第二步到最后一步那不懂= =平方差公式然后化简呀