Question

Народ помогите пж с алгеброй​

Answer 1

$\displaystyle\bf\\A_{x} ^{5} =72\cdot A_{x-2} ^{3} \\\\\\\frac{x!}{(x-5)!} =72\cdot\frac{(x-2)!}{(x-2-3)!} \\\\\\\frac{x!}{(x-5)!} =72\cdot\frac{(x-2)!}{(x-5)!} \\\\\\x!=72\cdot(x-2)!\\\\\\(x-2)!\cdot(x-1)\cdot x=72\cdot(x-2)!\\\\\\(x-1)\cdot x=72\\\\\\x^{2} -x-72=0\\\\Teorema \ Vieta:\\\\x_{1} =9\\\\x_{2} =-8<0-neyd\\\\Otvet:9$