NDA2017MathematicsDifferential EquationsActual
If x d y=y(d x+y d y) ; y(1)=1 and y(x) 0 , then what is y(-3) equal to?
Options
- A3
- B2
- C1
- D0
Correct answer
A. 3
Step-by-step solution
aligned & x d y=y d x+y^2 d y & x d y d x =y+y^2 d y d x & y-x d y d x y^2 = -d y d x aligned Integrating both sides x y =-y+c Given, x =1, y =1 aligned & 1 1 =-1+ c & c =2 & x y + y =2 & x + y ^2=2 y & -3+ y ^2-2 y =0 & y ^2-2 y -3=0 & y =3,-1 & y =3 aligned