Jika (1/9) pangkat x+3=3akar 8 pangkat 2x-1,nilai 81 pangkat x adalah

(1/9)^(x + 3) = ³√8^(2x - 1)
3^-2(x + 3) = 2^(3(2x - 1)/3)
-2(x + 3) = 2x - 1
-4x = 6 - 1
x = -5/4

81^x
= 3^4(-5/4)
= 3^-5
= 1/3^5
= 1/243