2 x a + 3 x b=
2 x b - a + 2 x c=
(a + 2 x c) x 4 =
16 x b + 28 x c - a =
15 x b - 8 x c =
21 x c x (4 x a + b)=

2xa+3xb=x(2a+3b)
2xb-a+2xc=2bx-a+2cx
(a+2xc)4=(a+2cx)*4=4a+8cx
16xb+28xc-a=16xb+28cx-a
15xb-8xc=x(15b-8c)
21xcx(4xa+b)21cx^2(4ax+b) =84acx^3+21bcx^2