Question

Phân tích thành nhân tử:

a) x²+4x-25y²+4

b) x³-4x²-8x+8

c) 4x²-3x-1 

Answer 1

a,\(x^2+4x-25y^2+4=\left(x^2+4x+4\right)-\left(5y\right)^2=\left(x+2\right)^2-\left(5y\right)^2\)

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

b, \(x^3-4x^2-8x+8=\left(x^3+8\right)-\left(4x^2+8x\right)\)

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

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

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

\(=\left(x-1\right)\left(4x+1\right)\)

Answer 2

Mk làm sai câu b nha , phảo làm như sau 

\(x^3-4x^2-8x+8=\left(x^3+8\right)-\left(4x^2+8x\right)\)

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

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

\(=\left(x+2\right)\left(x^2-6x+4\right)\)