Question

Решите неравенство 2x+1- 21x+39/x^2+x-2> =-1/x+2

Answer 1

 $2x+1- \frac{21x+39}{x^2+x-2} \geq \frac{-1}{x+2}\\\\2x+1- \frac{21x+39}{(x+2)(x-1)}+ \frac{1}{x+2} \geq 0\; ,\; \; x\ne -2\; ,\; x\ne 1\\\\ \frac{(2x+1)(x+2)(x-1)-21x-39+x-1}{(x+2)(x-1)} \geq 0\\\\ \frac{2x^3+3x^2-23x-42}{(x+2)(x-1)} \geq 0\\\\ \frac{(x+2)(x+3)(x-3,5)}{(x+2)(x-1)} \geq 0\\\\ \frac{(x+3)(x-3,5)}{x-1} \geq 0\\\\---(-3)+++(-2)+++(1)---(3,5)+++\\\\x\in [\, -3,-2)\cup (-2,1)$