Let the solution curve y=y(x) of the differential equation, [ x √x^2-y^2+e^ y x]x dy dx=x+[ x √x^2-y^2+e^ y x]y pass through the points (1,0) and (2α…
JEE Main 2022 — Mathematics Calculus
2022mcqhard
Let the solution curve y=y(x) of the differential equation, [x2−y2x+exy]xdxdy=x+[x2−y2x+exy]y pass through the points (1,0) and (2α,α),α>0. Then α is equal to
Official previous-year question
Held on 28 Jun 2022 · Verified 6 Jul 2026.
Options
A
21exp(6π+e−1)
B
21exp(3π+e−1)
C
exp(6π+e+1)
D
2exp(3π+e−1)
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Solution
Given x(x2−y2x+exy)dxdy=y(x2−y2x+exy)+x
Taking x common & cancelling them we get,
dxdy×(1−(xy)21+exy)=xy(1−(xy)21+exy)+1
Let y=vx⇒dxdy=v+xdxdv
(v+xdxdv)(1−v21+ev)=v(1−v21+ev)+1
v+xdxdV=v+(1−v21+ev)1
xdxdv=(1−v21+ev)1⇒(1−v21+ev)dv=xdx
Integrating both side we get,
⇒∫(1−v21+ev)dv=∫xdx
⇒sin−1v+ev=lnx+c⇒sin−1(xy)+exy=lnx+c
Now y(1)=0
⇒sin−1(10)+e0=ln1+c
⇒c=1
⇒sin−1(xy)+exy=lnx+1 ........(i)
Now y(2α)=α putting in equation (i) we get,
⇒sin−1(2αα)+e2αα=ln2α+1
⇒6π+e21=ln2α+1⇒α=21e6π+e−1
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