1、5a/6b²c-7b/12ac²+11c/8a²b
=20a³c/24a²b²c²-14ab³/24a²b²c²+33bc³/24a²b²c²
=(20a³c-14ab³+33bc³)/24a²b²c²
[2]22a+3+33-2a+2a+154a平方-9
=【2(2a-3)-3(2a+3)+15]/(4a²-9)
=-2a/(4a²-9）
【3】1x平方-4x+4-xx平方-4+12x+4
=1/(x-2)²-x/(x+2)(x-2)+1/2(x+2)
=[2x(x+2)-2x(x-2)+(x-2)²]/2(x+2)(x-2)²
=(x²+4x+4)/2x(x+2)(x-2)²
=(x+2)/2x(x-2)²
【4】1+ [ 3a-2]÷a+1a平方-4
=(a+1)/(a-2)×(a+2)(a-2)/(a+1)
=a+2