4) y'=[(2x)*(x²-2) - (x²+2)*2x]/(x²-2)²=
(2x³-4x-2x³-4x)/(x²-2)²=-8x/(x²-2)²
-----------------------------------------------------
5) y'=[(3x²+2x)*x - (x³+x²+16)*1]/x²=
(3x³+2x²-x³-x²-16)/x²=(2x³+x²-16)/x²
------------------------------------------------------
6) y'=[(6х+2)(2х+1)-(3х²+2х-1)*2]/(2x+1)²=
(12х²+4х+6х+2-6х²-4х+2)/(2х+1)²=
(6х²+6х+4)/(2х+1)².