If 3x - 3x-1 = 18, then the value of xx is Pick.
A) 3 B) 8 C) 27 D) 36 E) NOne
Sol.   3x - 3x-1 = 18   ⇔ 3x-1 (3 - 1) = 18   ⇔ 3x-1 = 9   ⇔ 32   ⇔ x-1 = 2   ⇔ x = 3.   ∴ xx = 33 = 27.   Answer 27
<result>C</result>
If 3x - 3x-1 = 18, then the value of xx is