a² -3ab + 3a - 9b =
= (a² -3ab) + (3a - 9b) =
= a·(a-3b) + 3·(a-3b) =
= (a-3b)·(a+3)
при a=1; b =- 1/3
(1-3·(-1/3))·(1+3) = (1+1)·(1+3) = 2 · 4 = 8
a² -3ab + 3a - 9b =
= (a² -3ab) + (3a - 9b) =
= a·(a-3b) + 3·(a-3b) =
= (a-3b)·(a+3)
при a=1; b =- 1/3
(1-3·(-1/3))·(1+3) = (1+1)·(1+3) = 2 · 4 = 8