Question

Phân tích đa thức thành nhân tử: (3x+1)² - 4(x-2)²

Answer 1

Ta có:

\(C_1:\left(3x+1\right)^2-4\left(x-2\right)^2=\left(9x^2+6x+1\right)-4\left(x^2-4x+4\right)\)

\(=9x^2+6x+1-4x^2+16x-16=5x^2+22x-15=5x\left(x+5\right)-3\left(x+5\right)=\left(5x-3\right)\left(x+5\right)\)

\(C_2:\left[\left(3x+1\right)-2\left(x-2\right)\right]\left[\left(3x+1\right)+2\left(x-2\right)\right]=\left(x+5\right)\left(5x-3\right)\)