``$6^{x-1}$ + $6^{x+2}$ = $6^{x-1}$ + $6^{x-2}$
``Vì:``
``$6^{x-1}$ . (1+$6^{3}$)``
``= $6^{x-1}$ . 1 + $6^{x-1}$ . $6^{3}$ (tính chất phân phối)``
``= $6^{x-1}$ + $6^{x-1+3}$ (phép nhân lũy thừa cùng cơ số)``
``= $6^{x-1}$ + $6^{x-2}$``
``⇒ $6^{x-1}$ + $6^{x-2}$ = $6^{x-1}$ + $6^{x-2}$``