Question

phân tích đa thức thành nhân tử

a)x²-x-56

b)4x²+8x-5

Answer 1

a: =(x-8)(x+7)

b: \(=4x^2+10x-2x-5=\left(2x+5\right)\left(2x-1\right)\)

Answer 2

a, \(x^2-x+\dfrac{1}{4}-\dfrac{1}{4}-56=\left(x-\dfrac{1}{2}\right)^2-\dfrac{225}{4}=\left(x-\dfrac{17}{2}\right)\left(x+7\right)\)

b, \(4x^2+8x+4-9=\left(2x+2\right)^2-9=\left(2x-1\right)\left(2x+5\right)\)

Answer 3

`a)x^2-x-56=x^2-8x+7x-56=x(x-8)+7(x-8)=(x-8)(x+7)`

`b)4x^2+8x-5=4x^2-2x+10x-5=2x(2x-1)+5(2x-1)=(2x-1)(2x+5)`