Question

phân tích đa thức thành nhân tử

a,\(2x^2+7x+5\)

b,\(x^3-2x-4\)

c,\(x^2+4x+3\)

d,\(16x-5x^2-3\)

Answer 1

Bài làm:

a) \(2x^2+7x+5=\left(2x^2+2x\right)+\left(5x+5\right)=2x\left(x+1\right)+5\left(x+1\right)\)

\(=\left(2x+5\right)\left(x+1\right)\)

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

\(=x^2\left(x-2\right)+2x\left(x-2\right)+2\left(x-2\right)=\left(x-2\right)\left(x^2+2x+2\right)\)

c) \(x^2+4x+3=\left(x^2+x\right)+\left(3x+3\right)=x\left(x+1\right)+3\left(x+1\right)\)

\(=\left(x+1\right)\left(x+3\right)\)

Answer 2

2x² + 7x + 5 = 2x² + 2x + 5x + 5 = ( 2x² + 2x ) + ( 5x + 5 ) = 2x( x + 1 ) + 5( x + 1 ) = ( 2x + 5 )( x + 1 )

x² + 4x + 3 = x² + x + 3x + 3 = ( x² + x ) + ( 3x + 3 ) = x( x + 1 ) + 3( x + 1 ) = ( x + 3 )( x + 1 )

Answer 3

Quên mất còn phần d:

\(16x-5x^2-3=\left(-5x^2+15x\right)-\left(x-3\right)=-5x\left(x-3\right)-\left(x-3\right)=\left(3-x\right)\left(5x+1\right)\)