[tex] \it a)\ \ x^2=1 \Longrightarrow \sqrt{x^2} = \sqrt1 \Longrightarrow |x| =1 \Longrightarrow x=\pm1\\ \\ \\b) \ \ 2x^2+1=-7|_{-1} \Longrightarrow 2x^2=-8|_{:2} \Longrightarrow x^2=-4 \Longrightarrow x^2 = 4\cdot(-1) \Longrightarrow \\ \\ \Longrightarrow x= \pm\sqrt{4\cdot(-1)} \Longrightarrow x= \pm2i [/tex]
[tex] \it c) \ \ x^2+2x^2=4x^2 \Longrightarrow 0=4x^2-x^2-2x^2 \Longrightarrow 0 = x^2 \Longrightarrow \\ \\\Longrightarrow x^2=0 \Longrightarrow x = 0 [/tex]
