a) x6 - x4 - 9x3 + 9x2
= x4.(x2 - 1) - 9x2(x - 1)
= x4.(x - 1)(x + 1) - 9x2.(x - 1)
= (x - 1).[x4.(x + 1) - 9x2]
= x2.(x - 1).[x2.(x + 1) - 9]
b) (xy + 4)2 - 4(x + y)2
= (xy + 4)2 - [2(x + y)]2
= [xy + 4 - 2(x + y)] . [xy + 4 + 2(x + y)]
c) (ab - xy)2 - (bx - ay)2
= [(ab - xy) - (bx - ay)] . [(ab - xy) + (bx - ay)]
= [ab - xy - bx + ay] . [ab - xy + bx - ay]
= [a.(b + y) - x.(b + y)] . [b(a + x) - y(a + x)]
= (a - x)(b + y).(b - y)(a + x)
Đúng 0
Bình luận (0)
