0\\t^2+2t-6=0\\D=28\\t_1= \sqrt{7} -1;\quad t_2=-1- \sqrt{7} \\\\3^x= \sqrt{7} -1\\x=\log_3( \sqrt{7} -1)" alt="9^x+2\cdot3^x+1-7=0\\\\9^x+2\cdot 3^x-6=0\\t=3^x>0\\t^2+2t-6=0\\D=28\\t_1= \sqrt{7} -1;\quad t_2=-1- \sqrt{7} \\\\3^x= \sqrt{7} -1\\x=\log_3( \sqrt{7} -1)" align="absmiddle" class="latex-formula">