a)
7x²-3x+2=0
∆=b²-4ac
∆=(-3)²-4(7*2)=9-4*14=9-56=-47<0
xe∅
b)
4x²-x-5≤0
∆=1+80=81 √∆=9
[tex]x_{1} = \frac{ 1 - 9 }{8} = \frac{ - 8}{8} = - 1 \\ x_{2} = \frac{1 + 9}{8} = \frac{10}{8} = 1 \frac{2}{8} = 1 \frac{1}{4} [/tex]
xe[-1, 1¼]
d)
36x²-6x>0 |:6
6x²-x>0
x(6x-1)>0
x>0 i 6x-1>0 u x<0 i x<⅙
6x>1 |:6
x>⅙
[tex]xe < - \infty ,0 > u < \frac{1}{6} , + \infty > [/tex]
