Let y = y x be a function of x satisfying y 1 - x 2 = k - x 1 - y 2 where k is a constant and y 1 2 = - 1 4 …

Let y=yx be a function of x satisfying y1-x2=k-x1-y2 where k is a constant and y12=-14.Then dydx at x=12 , is equal to
  1. -54
  2. -52
  3. 25
  4. 52

Solution

x=12,y=-14xy=-18

y.-2x21-x2+y'.1-x2=0-1.1-y2+x.-2y21-y2y'

-xy1-x2+y'1-x2=-1-y2+xy.y'1-y2

y'1-x2-xy1-y2=xy1-x2-1-y2

y'32+18.154=-18.34-154

y'45+1215=-1+4543

y'=-1523=-52

Asked in: JEE Main 2020 (07 Jan Shift 2)

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