a) \(x^2+7x+12\) \(=x^2+3x+4x+12\)
\(=x\left(x+3\right)+4\left(x+3\right)\)
\(=\left(x+4\right)\left(x+3\right)\)
b) \(=x^2+2x+4x+8\)
\(=x\left(x+2\right)+4\left(x+2\right)\)
\(=\left(x+4\right)\left(x+2\right)\)
c) \(=x^2-2x-8x+16\)
\(=x\left(x-2\right)-8\left(x-2\right)\)
\(=\left(x-8\right)\left(x-2\right)\)
d) \(=x^2-3x-5x+15\)
\(=x\left(x-3\right)-5\left(x-3\right)\)
\(=\left(x-5\right)\left(x-3\right)\)
Phân tích đa thức thành nhân tử :
a, x2+7x+12 = \(x^2+3x+4x+12=x\left(x+3\right)+4\left(x+3\right)\)
=\(\left(x+3\right)\left(x+4\right)\)
b, x2+6x+8\(=x^2+2x+4x+8=x\left(x+2\right)+4\left(x+2\right)\)
\(=\left(x+4\right)\left(x+2\right)\)
c, x2-10x+16
\(=x^2-2x-8x+16=x\left(x-2\right)-8\left(x-2\right)\)
\(=\left(x-8\right)\left(x-2\right)\)
d, x2-8x+15\(=x^2-3x-5x+15=x\left(x-3\right)-5\left(x-3\right)\)
\(=\left(x-5\right)\left(x-3\right)\)
