Jawabanmu

2014-09-02T20:28:42+07:00
Log18
=log(2×3×3)
=log2 + log3 +log3
=0.3010+0.4771+0.4771
=1.2552 

log21
=log7 + log3
=1.3222

log10,5
=log21/2
=log21-log2
=1.3222-0.3010
=1.0212

log1/7
=log1-log7
=0-0.8451
=(-0.8451)

Caranya gitu, tapi hasilnya cek lagi aja... Takut ada salah,..
2014-09-02T20:30:53+07:00
A. log18 -> (2 x 3 x 3)
= log2 + log3 + log3
= 0,3010 + 0,4771 + 0,4771
= 1,2552

b. log21 -> (3 x 7)
= log3 + log 7
= 0,4771 + 0,8451
= 1,3222

c. log10,5 -> (3 x 7 : 2)
= log3 + log7 - log2
=0,4771 + 0,8451 - 0,3010
= 1,0212

d. log1/7 -> (1 : 7)
= log1 - log7
= 0 - 0,8451
= -0,8451