因式分解（有步驟）２０分

1) ax-a[2]/a-b 　 + 　 bx-ab/b-a
= a(x-a)/a-b + b(x-a)/b-a
= a(x-a)-b(x-a)/a-b
= (a-b)(x-a)/a-b
= x-a

2) 1/a+b 　 - 　 3/2b
= 2b-3(a+b)/2b(a+b)
= 2b-3a-3b/2b(a+b)
= -3a-b/2b(a+b)
= -(3a+b)/2b(a+b)

3) x+4y/-2x(x-2y ) 　 + 　1/3x
= 3x(x+4y)-2x(x-2y)/-6x[2](x-2y)
= x[2]+16xy/-6x[2](x-2y)
= x(x+16y)/-6x[2](x-2y)
= x+16y/-6(x-2y)

4) 5/4x+6　 - 　 7/6x+9
= 5/2(2x+3) - 7/3(2x+3)
= 15-14/6(2x+3)
=1/6(2x+3)

5) 2x+y/x-y 　 + 　 y/2y-2x 　 - 　 x/x-y
= 2x+y/x-y - y/2(x-y) - x/x-y
= 2(2x+y) - y - 2x /2(x-y)
=4x+2y-y-2x/2(x-y)
=2x-y/2(x-y)