Question

大家帮帮忙！有一个步骤看不懂啊！急需帮助！

请问最后一个式子是怎么化出来的？

Answer 1

ax1/(x1^2 -1) - ax2/(x2^2 -1)
= ax1/[x1-1)(x1+1)] - ax2/[(x2-1)(x2+1)]
= ax1*(x2-1)(x2+1)/[(x1-1)(x1+1)(x2-1)(x2+1)] - ax2*(x1-1)(x1+1)/[(x2-1)(x2+1)(x1-1)(x1+1)]
= [ax1*(x2^2 -1) - ax2*(x1^2-1)]/[(x1-1)(x1+1)(x2-1)(x2+1)]
= a(x1x2^2 - x1 - x2x1^2 + x2)/........
= a(x1x2(x2-x1) + (x2-x1)/........
= a(x2-x1)(x1x2+1)/........