4x^2+12xy+9y^2+8x^2-12xy=12x^2+9y^2
12*3+9*4=36+36=72
(2х+3у)²+4х(2х-3у)=4x²+12xy+9y²+8x²-12xy=12x²+9y²
4x^2+12xy+9y^2+8x^2-12xy=12x^2+9y^2
12*3+9*4=36+36=72
(2х+3у)²+4х(2х-3у)=4x²+12xy+9y²+8x²-12xy=12x²+9y²