Differential Equations 3 Question 1

1. Given that the slope of the tangent to a curve y=y(x) at any point (x,y) is 2yx2. If the curve passes through the centre of the circle x2+y22x2y=0, then its equation is

(2019 Main, 8 April II)

(a) x2loge|y|=2(x1)

(b) xloge|y|=x1

(c) xloge|y|=2(x1)

(d) xloge|y|=2(x1)

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Answer:

Correct Answer: 1. (c)

Solution:

  1. Given, dydx=2yx2

dyy=2x2dx [integrating both sides]

loge|y|=2x+C

Since, curve (i) passes through centre (1,1) of the circle

x2+y22x2y=0loge(1)=21+CC=2

Equation required curve is

loge|y|=2x+2 [put C=2 in Eq. (i)] xloge|y|=2(x1)



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