((2x/(1-3y)+2x/(1+3y))/(2x(2x+7)/(9y²+1-6y))=
((1/(1-3y)+1/(1+3y))/((2x+7)/(9y²+1-6y))=
((1+3у+1-3у)/((1-3y)*(1+3y))*(1-3у)²/(2х+7))=2*(1-3у)²/((1-3у)*(1+3у)(2х+7))=
2*(1-3у)/(1+3у)(2х+7))=(2-6у)/(2х+7+6ху+21у)
