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If `xdy = y(dx + ydy); y(1) = 1 and y(x) > 0`, then what is `y(-3)` equal to?A. 3B. 2C. 1D. 0 |
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Answer» Correct Answer - a Given , `xdy = y (dx + ydy), y gt 0` ` rArr xdy - ydx = y^(2)dy ` ` rArr (xdy-ydx)/(y^(2)) = dy rArr d(x/y) = -dy` On integrating both sides , we get ` x/y = -y +C " "` …(i) Since , ` y (1) =1 rArr x = 1 , y =1` ` :. C = 2` Now , Eq, (i) becomes Again for x=-3 rArr ` -3 +y^(2) = 2Y` ` rArr y^(2) - 2y - 3 = 0` ` rArr (y+1)(y-3)=0` As `y gt 0` take y = 3 , neglecting y = -1 |
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