Let y=y(x) be the solution curve of the differential equation (1+ x) dydx+(y+1) x=0, y(0)=0. If the curve y=y(x) passes through the point ( , -12 ), then a value of is :
- 6
- 4
- 3
- 2
Answer
(4) 2
Solution
(1 + x) dydx + (y + 1) x = ddx [(1 + x)(y + 1) ] = 0
(1 + x)(y + 1) = C
Using y(0) = 0, (1)(1) = C, so C = 1.
The curve passes through ( , - 12 ), so (1 + ) 12 = 1
= 1 = 2 (one value)
Answer: (4)