x-1分之4-2x+1分之9
=[4(2x+1)-9(x-1)]/(x-1)(2x+1)
=(13-x)/(2x^2-x-1)
1-a+a+1分之a^2
=(1-a^2+a^2)/(a+1)
=1/(a+1)
请采纳.谢谢