DifferentiationHard
Question
If 2x = y1/5 + y-1/5, then (x2 - 1)
equals to
Options
A.5y
B.25 y
C.25 y2
D.y + 25
Solution
(y1/5 + y-1/5)2 = (y1/5 - y -1/5)2 + 4
Then y1/5 - y - 1/5 = 2
... (1)
Given y1/5 + y -1/5 = 2x ... (2)
From (1) & (2)
y = (x +
)5
Differentiating both sides w.r.t. x, we get

or (x2 - 1)
= 25y2
Again differentiating w.r.t. x,
2x
+ 2(x2 - 1)
= 50 y 
Dividing by 2
on both sides
x
+ (x2 - 1)
= 25y 
Then y1/5 - y - 1/5 = 2
Given y1/5 + y -1/5 = 2x ... (2)
From (1) & (2)
y = (x +
Differentiating both sides w.r.t. x, we get
or (x2 - 1)
Again differentiating w.r.t. x,
2x
Dividing by 2
x
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