Question

Buna dimineata, imi poate arata cineva cum pot sa rezolv aceste exerciti, rapid va rog.​

Answer 1

17.

$\it 3^{x^2+x}=9\ \Leftrightarrow\ 3^{x^2+x}=3^2\ \Leftrightarrow\ x^2+x=2\ \Leftrightarrow\ x(x+1)=2=\\ \\ =(-2)\cdot(-1)=1\cdot2;\ \ \ S=\{-2,\ \ 1\}$

18.

$\it 3^x+3^{-x}=\dfrac{10}{3} \Rightarrow 3^x+\dfrac{1}{3^x}=3+\dfrac{1}{3} \Rightarrow x=\pm1$

19.

$\it 2^{x^2+x+1}=8 \Rightarrow2^{x^2+x+1}=2^3 \Rightarrow x^2+x+1=3\bigg|_{-1} \Rightarrow x^2+x=2 \Rightarrow \\ \\ \Rightarrow x(x+1)=2=(-2)\cdot(-1)=1\cdot2 \Rightarrow \ S=\{-2,\ \ 1\}$