X-1 5-х 3х
__ x 20 = __ х 20 + __ х 20
5 2 4
__ x 20 = __ х 20 + __ х 20
5 2 4
4(х-1) = 10(5-х) + 5(3х)
4х-4=50-10х+15х
4х+10х-15х=50+4
-1х=54
х=-54
упр.6
3x(x+y+c)-3y(x-y-c)-3c(x+y-c)= 3x^2+ 3xy+3xc-3xy+3y^2+3yc-3xc-3yc+3c^2=3x^2+3y^2+3c^2