我求o下你地...你地幫o下我....(關於M&S)

我有幾條二階導數唔識做.....試左好多次都做唔倒........希望M&S高手可以幫o下我......萬分感激.....!!!!!
1.設y=t^1/2 - 1/t^1/2+1 (即係y等於t^1/2 -1 over t^1/2 +1)求當t=1,dy/dt及d^2y/dt^2的值

2.一條曲線的方程為y^3-xy-1=0
(a)求dy/dx
(b)求d^2y/dx^2
(c)求在點(2,-1)處d^2y/dx^2的值

3.若y=[x+(x^2-1)^1/2]^2,
證明(x^2-1)d^2y/dx^2 + x(dy/dx) -4y=0

麻煩o係解答ge時候列出步驟....等我可以明白點樣計.....多謝各位得力相助~~
P.S第1題條式其實係將t開方....所以寫左做t^1/2.....而-1係另外的....所以唔好誤會係t的1/2-1次方............