Question

решите неравенство 6,6-0,8x-x^2>0

Answer 1

6,6 - 0,8x - x² > 0

5x² + 4x - 33 < 0

5x² + 4x - 33 = 0

$D=4^{2}-4*5*(-33)=16+660=676=26^{2}\\\\x_{1}=\frac{-4+26}{10}=2,2\\\\x_{2}= \frac{-4-26}{10}=-3\\\\ 5x^{2} +4x-33=5(x-2,2)(x+3)$

5(x - 2,2)(x + 3) < 0

(x - 2,2)(x + 3) < 0

____+_______(- 3)_______ - __________(2,2)_________+________

x ∈ (- 3 ; 2,2)