Phân tích đa thức thành nhân tử :
a) \(2,5x^2+3,7x+1,2\)
\(=2,5x^2+2,5x+1,2x+1,2\)
\(=\left(2,5x^2+2,5x\right)+\left(1,2x+1,2\right)\)
\(=2,5x\left(x+1\right)+1,2\left(x+1\right)\)
\(=\left(2,5x+1,2\right)\left(x+1\right)\)
b) \(4x^3+6x^2+9x+7\)
\(=4x^3+4x^2+2x^2+2x+7x+7\)
\(=\left(4x^3+4x^2\right)+\left(2x^2+2x\right)+\left(7x+7\right)\)
\(=4x^2\left(x+1\right)+2x\left(x+1\right)+7\left(x+1\right)\)
\(=\left(4x^2+2x+7\right)\left(x+1\right)\)