Question

Решите уравнение:)

5х^-2 +7х^-1 +2=0​

Answer 1

$5x^{-2}+7x^{-1}+2=0$

Сделаем замену :

$x^{-1}=m\\\\5m^{2}+7m+2=0\\\\D=7^{2}-4*5*2=49-40=9=3^{2}\\\\m_{1}=\frac{-7-3}{10}=-1\\\\m_{2}=\frac{-7+3}{10}=-\frac{2}{5}\\\\1)x^{-1}=-1\\\\\frac{1}{x}=-1\\\\x_{1} =-1\\\\2)x^{-1}=-\frac{2}{5}\\\\\frac{1}{x}=\frac{-2}{5}\\\\-2x=5\\\\x_{2}=-2,5$