Question

2х²-х-5= разложите на множители
даю 20 баллов​

Answer 1

Ответ:

$2x^2-x-5=0\ \ ,\ \ \ D=1+4\cdot 2\cdot 5=41\ \ ,\ \ x_{1,2}=\dfrac{1\pm \sqrt{41}}{4}\\\\\\2x^2-x-5=2\cdot \Big(x-\dfrac{1-\sqrt{41}}{4}\Big)\Big(x-\dfrac{1+\sqrt{41}}{4}\Big)=\\\\\\=\Big(2x-\dfrac{1-\sqrt{41}}{2}\Big)\Big(x-\dfrac{1+\sqrt{41}}{4}\Big)=\dfrac{4x-1+\sqrt{41}}{2}\cdot \dfrac{4x-1-\sqrt{41}}{4}=\\\\\\=\dfrac{1}{8}\cdot \Big(4x-1+\sqrt{41}\Big)\Big(4x-1-\sqrt{41}\Big)$