РЕШИТЕ ДВА ЗАДАНИЯ! ВСЕГО 2! ПЖ.

3. $\frac{b+4}{b} \ \textless \ \frac{5-2b}{3}$
$\frac{b+4}{b} - \frac{5-2b}{3} \ \textless \ 0$
$\frac{3b+12-5b+2b^{2} }{3b} \ \textless \ 0$
$\frac{2b^{2}-2b+12}{3b} \ \textless \ 0$
2b²-2b+12=0
b²-b+6=0
D=1-24= -23 ⇒b²-b+6>0
3b<0, b≠0<br>b<0<br>5. $\sqrt{5a-1} + \sqrt{a+7}$
$\left \{ {{5a-1 \geq 0} \atop {a+7 \geq 0}} \right.$
$\left \{ {{5a \geq 1} \atop {a \geq -7}} \right.$
$\left \{ {{a \geq 0,2} \atop {a \geq -7}} \right.$
a∈[0,2;+∞)