5(3-5x)²-5(3x-7)(3x+7)
(a+1)²+3(a-1)²-5(a-1)(a+1)
(x-1)²-4(x+1)²-6(x+1)(x-1)

5(3-5x)²-5(3x-7)(3x+7)=5(9-30х+25х²)-5(9х²-49)=45-150х+125х²-45х²+245==80х²-150х+290(a+1)²+3(a-1)²-5(a-1)(a+1)=а²+2а+1+3(а²-2а+1)-5(а²-1)=а²+2а+1+3а²-6а+3--5а²+5=-а²-4а+9(x-1)²-4(x+1)²-6(x+1)(x-1)=х²-2х+1-4(х²+2х+1)-6(х²-1)=х²-2х+1-4х²-8х-4--6х²+6=-9х²-10х+3