Question

Phân tích đa thức thành nhân tử:

a)3x² - 2x -5

b) x² - 6x -40

Answer 1

a) 3x²-2x-5

= 3x²+3x-5x-5

= (3x²+3x)-(5x-5)

= 3x(x+1)- 5(x+1)

= (x+1)(3x-5)

b) x²-6x-40

= x²+4x-10x-40

= (x²+4x)-(10x-40)

= x(x+4)- 10(x+4)

= (x+4)(x-10)

Answer 2

a. \(3x^2-2x-5=5x^2-5-2x^2-2x=5\left(x^2-1\right)-2x\left(x-1\right)=5\left(x-1\right)\left(x+1\right)-2x\left(x+1\right)=\left(x+1\right)\left[5\left(x-1\right)-2x\right]=\left(x+1\right)\left(3x-5\right)\)

b. \(x^2-6x-40=x^2+4x-10x-40=x\left(x+4\right)-10\left(x+4\right)=\left(x+4\right)\left(x-10\right)\)