jika f(x)= 3^x-1, nilai f^-1(81)=... tolong bantu yaaa

Kelas 10 Matematika
Bab Fungsi Komposisi

^ = pangkat

f(x) = 3^(x - 1)
y = 3^(x - 1)
x - 1 = ³log y
x = 1 + ³log y
f⁻¹ (x) = 1 + ³log x

f⁻¹ (81) = 1 + ³log 81
f⁻¹ (81) = 1 + ³log 3⁴
f⁻¹ (81) = 1 + 4 . ³log 3
f⁻¹ (81) = 1 + 4
f⁻¹ (81) = 5