Question

Решите через дискриминант
x^2-7x-18<0
-6x^2+13x-5≤0
x^2-6x-7=0

Answer 1

1. 
$x^{2} -7x-18 textless 0 \ \ D=(-7)^2-4*(-18)=121 textgreater 0 \ \ x1= frac{7+11}{2}=9 \ x2= frac{7-11}{2}=-2$
(-2; 9)
2.
$-6x^2+13x-5 leq 0 \ D=13^2-4*(-6)*(-5)=49 textgreater 0 \ x1= frac{-13+7}{2*(-6)} =0.5 \ x2= frac{-13-7}{2*(-6)}=1 frac{2}{3}$
$[0.5; 1 frac{2}{3}]$
3.
$x^{2} -6x-7=0 \ D=-6^2-4*1*(-7)=64 textgreater 0 \ x1= frac{6+8}{2} =7 \ x2= frac{6-8}{2} =-1$
Ответ: -1, 7