問3題數學題!!! 10~~~~~~~~~~~~~~~~~~~~~

1. => 15c² /d³ * d/5c * d²/9c = 3c/d² * d²/9c = 1/3

2. => 1-5x/5y 除 4-20x/10y = 1-5x/5y * 10y/4-20x = 1-5x/2-10x = 1/2

3. => (4m-1)²/15-5n 除 (4m-1)X n²-3²/n-4mn = (4m-1)/15-5n X n²-3²/n-4mn
= (4m-1)/ [5(3-n)] X { [(n+3)(n-3)] / n(1-4m)}
= -(1-4m)/[5(3-n)] X { [(n+3)(n-3)] / n(1-4m)}
= -1/[5(3-n)] X { [(n+3)(n-3)] / n}
= 1/[5(n-3)] X { [(n+3)(n-3)] / n}
= 1/5 X (n+3)/n
= (n+3)/5n