a) x³-9x²-4x-36=0

⇔ x²(x-9)-4(x-9)=0

⇔ (x-9)(x²-4)=0

⇒ Xảy ra 2 trường hợp:

- TH1: x-9=0 ⇔ x=9

- TH2: x²-4=0 ⇔ x=2 hoặc x=-2

Vậy x=9 hoặc x=2 hoặc x=-2.

ax-bx-a²y-b²y

=x(a-b)-y(a²-b²)

=x(a-b)-y(a-b)(a+b)

=(a-b)[x-y(a+b)]

Mik làm tạm thế ko bt có đúng ko

Đúng thì tick nhé

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