Question

Care știe sa rezolve măcar câteva ex , dau coroana

Answer 1

$\mathbf {14.}\ \ \it a)\ 2(x+5)+5=25|_{-5} \Rightarrow 2(x+5)=20|_{:2} \Rightarrow x+5=10 \Rightarrow x=5\\ \\ \\b)\ \dfrac{\overline{x7}}{25}<1 \Rightarrow \overline{x7}<25 \Rightarrow x=1\\ \\ \\ \it c)\ \dfrac{3}{8}\leq\dfrac{2}{2a+1}\leq\dfrac{2}{3} \Rightarrow \dfrac{3}{2}\leq\dfrac{2a+1}{2}\leq\dfrac{8}{3}|_{\cdot6} \Rightarrow 9\leq6a+3\leq16|_{-3} \Rightarrow \\ \\ \\ \Rightarrow 6\leq6a\leq15|_{:6} \Rightarrow 1\leq a\leq2,5 \Rightarrow a\in\{1,\ \ 2\}$