Question

двойные неравенства сроочно !!!

Answer 1

1) 
$1 leq frac{5+x}{2} textless  2.5$
$1*2 leq frac{5+x}{2}*2 textless  2.5*2$
$2leq 5+x textless  5$
$2-5leq 5+x -5 textless  5-5$
$-3 leq x textless  0$
$[-3;0)$

2) 
$0 textless frac{2x+3}{5} textless 1$
$0*5 textless frac{2x+3}{5}*5 textless 1*5$
$0 textless 2x+3 textless 5$
$0 -3 textless 2x+3-3 textless 5-3$
$-3 textless 2x textless 2$
$frac{-3}{2} textless frac{2x}{2} textless frac{2}{2}$
$-1.5 textless x textless 1$
$(-1.5;1)$

3) 
$2.15 textless frac{3x-1}{4} textless 2.6$
$2.15*4 textless frac{3x-1}{4}*4 textless 2.6*4$
$8.6 textless 3x-1 textless 10.4$
$8.6+1 textless 3x-1+1 textless 10.4+1$
$9.6 textless 3x textless 11.4$
$frac{9.6}{3} textless frac{3x}{3} textless frac{11.4}{3}$
$3.2 textless x textless 3.8$
$(3.2;3.8)$

4) 
$-1 textless frac{3x-1}{4} textless 2$
$-1 *4 textless frac{3x-1}{4}*4 textless 2*4$
$-4 textless 3x-1 textless 8$
$-4+1 textless 3x-1+1 textless 8+1$
$-3 textless 3x textless 9$
$frac{-3}{3} textless frac{3x}{3} textless frac{9}{3}$
$-1 textless x textless 3$
$(-1;3)$