Example 4 (Index Equation – Substitution) 4 Feb,2014 userLeave a comment Example 4 Solve each of the following. (a) ${3}^{x-1}+{3}^{x}=12$ (b) ${2}^{x}+{2}^{x+3}=72$ (c) ${4}^{x+1}+{2}^{2x}=20$