(a+2x)/a-1/b=(b+2)x/ab+1(b≠2) 两边同时乘以ab得
b(a+2x)-a=(b+2)x+ab (b≠2)
ab+2bx-a=(b+2)x+ab (b≠2)
2bx-(b+2)x=ab-ab+a (b≠2)
(b-2)x=a (b≠2)
x=a/(b-2) (b≠2)