If x2+y2=t−1tand x4+y4=t2+1t2, then x3ydydx=

$x^{2} + y^{2} = t - \frac{1}{t}, x^{4} + y^{4} = t^{2} + \frac{1}{t^{2}}$

$x^{4} + y^{4} + 2 x^{2} y^{2} = t^{2} + \frac{1}{t^{2}} - 2$

$t^{2} + \frac{1}{t^{2}} + 2 x^{2} y^{2} = t^{2} + \frac{1}{t^{2}} - 2$

$x^{2} y^{2} = - 1 \dots \dots (1)$

Differentiate with respect to $' x'$

$2 x . y^{2} + x^{2} .2 y . y^{|} = 0$

$x^{2} y y^{|} = - x y^{2}$

$\Rightarrow x^{3} y . y^{|} = - {(x y)}^{2}$ [from (1)]

$= - (- 1)$

$= 1$

If $x^{2} + y^{2} = t - \frac{1}{t}$ and $x^{4} + y^{4} = t^{2} + \frac{1}{t^{2}}$ , then $x^{3} y \frac{d y}{d x} =$