Решите уравнения !!!! 2 сверху

Решите задачу:

$5^{2x}-5^x-600=0\\5^x=t,\,\,\,t\ \textgreater \ 0\\t^2-t-600=0\\D=1+4*600=1+2400=2401=49^2\\\\t_1=\frac{1+49}2=25\\\\t_2=\frac{1-49}2=-24\,\,(need\,\,t\ \textgreater \ 0)\\\\5^x=25\\5^x=5^2\\x=2$

$3^x+9^{x-1}-810=0\\3^x+\frac{3^{2x}}9-810=0\\3^{2x}+9*3^x-7290=0\\3^x=t,\,\,t\ \textgreater \ 0\\t^2+9t-7290=0\\D=81+4*7290=81+29160=29241=171^2\\\\t_1=\frac{-9+171}2=81\\\\t_2=\frac{-9-171}2=-90\,\,(need\,\,t\ \textgreater \ 0)\\\\t=81\\3^x=3^4\\x=4$