ПОМОГИТЕ СРОЧНО!!!y=3x-1/х^2 -1 y=cos(2x^2 +1)

Решите задачу:

$y'=( \frac{3x-1}{ x^{2} -1} )'= \frac{(3x-1)'*( x^{2} -1)-( x^{2} -1)'*(3x-1)}{( x^{2} -1) ^{2} } =$
$= \frac{3*( x^{2} -1)-2x*(3x-1)}{( x^{2} -1) ^{2} } = \frac{3 x^{2} -3-6 x^{2} +2x}{ ( x^{2} -1)^{2} }} = \frac{-3 x^{2} +2x-3}{ ( x^{2} -1)^{2} }$

$y'=(cos(2x^{2} +1))'=-sin(2 x^{2} +1)*(2x^{2} +1)'=$
$=-sin(2 x^{2} +1)*(2*2x)=-4x*sin(2 x^{2} +1)$