Let y=y(x) be the solution of the differential equation dydx= (1+x+x2 ) (1-y+y2 ), y(0)= 12. Then (2y(1)-1) is equal to :
- 3 ( 11 36 )
- 32 ( 11 312 )
- 3 ( 11 312 )
- 32 ( 11 36 )
Answer
(3) 3 ( 11 312 )
Solution
Separating the variables: dyy2-y+1=(1+x+x2) dx
y2-y+1= (y- 12 )2+ ( 32 )2
2 3 -1 ( 2y-1 3 )=x+ x22+ x33+C
y(0)= 12 -10=0 C=0
At x=1: 2 3 -1 ( 2y(1)-1 3 )=1+ 12+ 13= 116
-1 ( 2y(1)-1 3 )= 11 312
2y(1)-1= 3 ( 11 312 )
Answer: (3)