一條中二既數...好多中6-7既人都唔識(到e家仲未解)10分!!

Ｐ= mgh ( h - x )
h - x = mgh / P
h - x = mg/P ( h )
( h - x ) / h = mg/P
h/h - x/h = mg/P
1 - x/h = mg/P
x/h = 1 - mg/P
x/h = ( P - mg ) / P
h ( P - mg ) = xP ... 交义相乘
h = xP / ( P - mg )

這個最佳回答第一步已經錯了！請留意一下：
P=mgh(h-x)下一步頂多是:
1/(h-x)=mgh/P
不過這樣都是計不到的
但至少要知道這個答案不是對的!!!!!!

the answer by y99shto is correct

Ｐ= mgh ( h - x )
h - x = mgh / P ??????????
(你計錯數了，應該是︰h-x = P / mgh)

Ｐ=mgh(h-x)
P/h-x=mgh
P=(mgh)(h-x)
P=h(mg‧-x)
h=P/-mgx

I'll use a method called "completing square". This method does not require quadratic formula. Thus a form two student can easily understand.

h(h-x)=P/mg
h^2 - 2(x/2)h + (x/2)^2 = P/mg + (x/2)^2 <---Add (x/2)^2 on both sides
(h - x/2)^2 = (4P+mg)/4mg
Square rooting both sides,
h-x/2 = 士√{(4P+mg)/4mg}
h = x/2 士 √{(4P+mg)/4mg}

Thus the answer is h = x/2 士 √{(4P+mg)/4mg}

這是一條二次方程 (quadratic equation)，用配的方法可解。

P =mgh(h-x)

mg(h² - hx) = P

mg[h² - 2h(x/2) + (x/2)² - (x/2)²] = P

mg(h - x/2)² - mg(x/2)² = P

mg(h - x/2)² - mgx²/4 = P

mg(h - x/2)² = P + mgx²/4

mg(h - x/2)² = (4P + mgx²)/4

(h - x/2)² = (4P + mgx²)/4mg

h - x/2 = ±√[(4P + mgx²)/4mg]

h = x/2 ± √[(4P + mgx²)/4mg]

h = x/2 + √[(4P + mgx²)/4mg] 或 h = x/2 - √[(4P + mgx²)/4mg]

P/(h-x)=mgh
p/h-p/x=mgh
p-ph/x=mghh
px/x-ph/x=mghh
p(x-h)/x=mghh
x-h=mghhx/p
.....

唔識

係咪物理來架?
mgh

係先有得計
唔係就真係唔識