factorize〖3(x+1)〗^2-7(x+1)+2

take u=x+1
3u^2-7u+2=0
u=2 or u=1/3
then x=1 or x=-2/3

Method1：
3 (x+1)² - 7(x+1) + 2
= [3(x+1) - 1][ (x+1) - 2]
= (3x+3-1)(x+1-2)
= (3x+2)(x-1)

Method2：
3 (x+1)² - 7(x+1) + 2
= 3 (x² + 2x + 1) - 7x - 7 + 2
= 3x² + 6x + 3 - 7x - 5
= 3x² - x - 2
= (3x+2)(x-1)

[3(x＋1)]^2 - 7(x＋1)＋2
＝ (3x＋3)^2 - 7x－7＋2
＝9x^2 ＋ 18x＋9 - 7x－5
＝9x^2 ＋11x ＋4