If y = y(x) is the solution of the differential equation, 4 - x2 dydx = ( ( -1 ( x2 ) )2 - y ) -1 ( x2 ), -2 x 2, y(2) = 2 - 84, then y2(0) is equal to .
Answer
4
Solution
Let u = -1 x2 dudx = 1 4 - x2
dydu = (u2 - y)u
dydu + uy = u3 (linear)
I.F. = e u du = eu2/2
y eu2/2 = u3 eu2/2 du
Put u22 = w u du = dw:
2w ew dw = 2(w - 1)ew
y = u2 - 2 + Ce-u2/2
At x = 2: u = 2, y = 24 - 2
24 - 2 = 24 - 2 + Ce- 2/8 C = 0
y = ( -1 x2 )2 - 2
y(0) = -2 y2(0) = 4
Answer: 4