Question

Phân tích đa thức thành nhân tử:

a)9(a+b)^2-4(a-2b)^2

b)9x^6-12x^7+4x^8

c)8x^6-27y^3

d)1/64x^6-125y^3

Answer 1

a) \(9\left(a+b\right)^2-4\left(a-2b\right)^2\)

\(=\left(3a+3b\right)^2-\left(2a-4b\right)^2\)

\(=\left(3a+3b-2a+4b\right)\left(3a+3b+2a-4b\right)\)

\(=\left(a+7b\right)\left(5a-b\right)\)

b) \(9x^6-12x^7+4x^8\)

\(=x^6\left(9-12x+4x^2\right)\)

\(=x^6\left(2x-3\right)^2\)

c) \(8x^6-27y^3\)

\(=\left(2x^2\right)^3-\left(3y\right)^3\)

\(=\left(2x^2-3y\right)\left(4x^4+6x^2y+9y^2\right)\)

d) \(\frac{1}{64}x^6-125y^3\)

\(=\left(\frac{1}{4}x^2\right)^3-\left(5y\right)^3\)

\(=\left(\frac{1}{4}x^2-5y\right)\left(\frac{1}{16}x^4+\frac{5}{6}xy+25y^2\right)\)