解方程（6x+7)的平方乘（3x+4)(x+1)=6 要看得懂.

令t=6x+7,方程化为：t^2 (6x+8)(6x+6)=6*2*6即t^2(t+1)(t-1)=72t^2(t^2-1)=72t^4-t^2-72=0(t^2-9)(t^2+8)=0所以有：t^2-9=0, 当t=3,6x+7=3, x=-2/3当t=-3, 6x+7=-3, x=-5/3即有两个实数-2/3, -5/3....