Question

Phân tích đa thúc thành nhân tử:

a) 16x - 5x ² - 3

b) x ² - 4x - 5

c) x ⁴ + x ³ + x + 1

d) x ⁴ - x ³ - x ² + 1

e) x ⁴ + 4x ² - 5

 

Answer 1

a> \(16-5x^2-3\)

\(=-5x^2+16x-3\)

\(=-5x^2+x+15x-3\)

\(=-x\left(5x-1\right)+3\left(5x-1\right)\)

\(=\left(5x-1\right)\left(3-x\right)\)

Answer 2

b> \(x^2-4x-5\)

\(=x^2-5x+x-5\)

\(=\left(x^2+x\right)-\left(5x+5\right)\)

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

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

Answer 3

c> \(x^4+x^3+x+1\)

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

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

\(=\left(x+1\right)\left(x+1\right)\left(x^2-x+1\right)\)

\(=\left(x+1\right)^2\left(x^2-x+1\right)\)

Answer 4

d> \(x^4-x^3-x^2+1\)

\(=x^3\left(x-1\right)-\left(x^2-1\right)\)

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

\(=\left(x-1\right)\left[x^3-\left(x+1\right)\right]\)

\(=\left(x-1\right)\left(x^3-x-1\right)\)

Answer 5

cái này thì dùng phương pháp nhẩm nghiệm nhá bn