Question

Помогите пожалуйста срочно алгебра 9 класс​

Answer 1

$\displaystyle\bf\\A_{x} ^{2} =20\\\\\\\frac{x!}{(x-2)!} =20\\\\\\\frac{(x-2)!\cdot(x-1)\cdot x}{(x-2)!} =20\\\\\\(x-1)\cdot x=20\\\\x^{2} -x-20=0\\\\Teorema \ \ Vieta:\\\\x_{1} =5\\\\x_{2} =-4-neyd\\\\Otvet:5$