[tex] 4^{n+3} = 8^6\\ \\ (2^2)^{n + 3} = (2^3)^6\\ \\ 2^{2n + 6 } = 2^{18}\\ \\ 2^{2n} = 2^{18 - 6} = 2^{12}\\ \\ n = 12 : 2 \\ \\n = 6\\ \\ \\ \\ \\4^n + 4^{n+1}+4^{n+2} = 21 \\ \\4^n(1 + 4 + 4^2 ) = 21\\ \\ 4^n(5 + 16 ) = 21 \\ \\ 4^n * 21 = 21 \\ \\ 4^n = 21: 21 \\ \\ 4^n = 1\\ \\4 ^n = 4^0\\ \\n = 0 [/tex]
