10-4(2x+5)=6y-13
4y-63=5(4x-2y)+2
4y-63-20x+10y-2=0
14y-65-20x=0
x=0.7y-3.25
3-8x-6y=0
3-8*(0.7y-3.25)-6y=0
3-5.6y+26-6y=0
29-11.6y=0
y=29/11.6y=2.пятых
14*2.5-65-20x=0
-30-20x=0
x=-30/20
x=-1.5
2) -y(2+a) +x(2+a) = (x-y)(2+a)
3) x^2 - (8^2) = (x-8)(x+8)
4) (3a)^2 - (4a)^2 = (3a - 4a)(3a+4a)