Question

Bài 1:  phân tích đa thứ thành nhân tử

 a) ( x - 12 )(x + 7 ) - 2x + 14

b) x² - 6x + 8

c) 9x² + 9xy - ( x + y )

d) ( x²  - 2xy + y² ) - 81

e) ( x + 4 )² - 15 ( 4 - x)

 

 

Answer 1

Answer 2

a) \(=x^2+7x-12x-84-2x+14\)

\(=x^2-7x-70\)

b)\(=x^2-4x-2x+8\)

\(=x\left(x-4\right)-2\left(x-4\right)\)

 \(=\left(x-4\right)\left(x-2\right)\)

c) \(=9x\left(x+y\right)-\left(x+y\right)\)

\(=\left(9x-1\right)\left(x+y\right)\)

d)\(=\left(x-y\right)^2-9^2\)

\(=\left(x-y+9\right)\left(x-y-9\right)\)

e)\(=x^2+8x+16-60+15x\)

\(=x^2+23x-44\)

Answer 3

a) Ta có: \(\left(x-12\right)\left(x+7\right)-2x-14\)

\(=\left(x-12\right)\left(x+7\right)-2\left(x+7\right)\)

\(=\left(x+7\right)\left(x-14\right)\)

b) Ta có: \(x^2-6x+8\)

\(=x^2-2x-4x+8\)

\(=\left(x-2\right)\left(x-4\right)\)

c) Ta có: \(9x^2+9xy-\left(x+y\right)\)

\(=9x\left(x+y\right)-\left(x+y\right)\)

\(=\left(x+y\right)\left(9x-1\right)\)

d) Ta có: \(\left(x^2-2xy+y^2\right)-81\)

\(=\left(x-y\right)^2-81\)

\(=\left(x-y-9\right)\left(x-y+9\right)\)