3 8*b - 4*b
8*b^3 - 4*b при b = 3/2
8*b^3 - 4*b
8*(3/2)^3 - 4*(3/2)
8*(3/2)^3 - 4*3/2
21
8.0*b^3 - 4.0*b
/ 2\ 4*b*\-1 + 2*b /