计算题~~~!

(1)1/2a－1/(a+b)*[(a+b)/2a－(2a^2+2ab)/2a]
=1/2a－1/(a+b)*[(a+b)-(2a^2+2ab)]/2a
=1/2a－1/(a+b)*[(a+b)-2a(a+b)]/2a
=1/2a－[1/(a+b)]*(a+b)(1-2a)/2a
=1/2a-(1-2a)/2a
=(1-1+2a)/2a
=2a/2a
=1

(2)a^2/(a^2+2a)*[a^2/(a-2)－4/(a-2)]
=[a^2/(a^2+2a)]*[(a^2-4)/(a-2)]
=[a^2/(a^2+2a)]*[(a+2)(a-2)/(a-2)]
=[a^2/a(a+2)]*(a+2)
=a

(3)1/(x-2)－(1-x)/(2-x)=-3
1/(x-2)+(1-x)/(x-2)=-3
(1+1-x)/(x-2)=-3
(2-x)/(x-2)=-3
-1=-3
不成立
方程无解

(4)(x+2)/(x+1)-2=(x+3)/(1-x)
两边乘(x+1)(1-x)
(x+2)(1-x)-2(1+x)(1-x)=(x+3)(x+1)
-x^2-x+2-2+2x^2=x^2+4x+3
-x=4x+3
5x=-3
x=-3/5
分式方程要检验
经检验，x=-3/5是方程的解