计算或化简; ①a-b分之b 减去a-b分之a ②y-x分之1 加上 2y-2x分之1 ③5a分之12xy除以8x的平方

①a-b分之b 减去a-b分之a
= b/(a-b) - a/(a-b)
= (b-a)/(a-b)
= -1
②y-x分之1 加上 2y-2x分之1
= 1/(y-x)+1/(2y-2x)
= (2+1)/(2y-2x)
= 3/(2y-2x)
③5a分之12xy除以8x的平方y
= 12xy/(5a) ÷ 8x^2y
= 12xy/(5a×8x^2y)
= 3/(10ax)
④（3y分之2x)的平方 乘以 （4x分之3y)的平方
= [2x/(3y)]^2 × [3y/(4x)]^2
= [ 2x/(3y) × 3y/(4x) ]^2
= [ 1/2 ]^2
= 1/4