- Mình nhầm sửa lại nè : )
Ta có : \(9x^2+6x-5\)
= \(\left(3x+1\right)^2-6\)
= \(\left(3x+1\right)^2-\left(\sqrt{6}\right)^2\)
= \(\left(3x+1-\sqrt{6}\right)\left(3x+1+\sqrt{6}\right)\)
Ta có : \(9x^2+6x-5\)
= \(\left(3x\right)^2+2.3x+4-9\)
= \(\left(3x+2\right)^2-9\)
= \(\left(3x+2-3\right)\left(3x+2+3\right)\)
= \(\left(3x-1\right)\left(3x+5\right)\)