CBSE Class 12 Math 2012 Solved Paper

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Question : 12
Total: 29
Solve the following differential equation:
2x2
dx
dy
- 2xy + y2 = 0
Solution:  
Here,
2x2
dx
dy
- 2xy + y2 = 0
dy
dx
=
2xyy2
2x2

Hence the given equation is an homogeneous equation.
Let y = vx
and
dy
dx
= y + x
dv
dx

So, v + x
dv
dx

So, v + x
dv
dx
=
2x(vx)(vx)2
2x2

=
2vv2
2
= v
v2
2

⇒ x
dv
dx
= -
v2
2

⇒ 2 ∫
1
v2
dv = ∫
dx
x

⇒ 2 (
1
v
)
= - log |x| + c
2x
y
= log |x| + c
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