2. Diketahui ²log 3 = a dan ⁷log 4 = b , maka ⁶log 63 =
1. Nilai x yang memenuhi ²log² 3x+ 2 ²log 3x – 3 = 0 adalah
Jawaban:
1. ²log²3x + 2 ²log3x – 3 = 0
misal : p = ²log3x
p² + 2p – 3 = 0
(p + 3) (p – 1) = 0
p = -3 atau p = 1
²log3x = -3 atau ²log3x = 1
Inget bahwa ^a log b = c equivalen dg
a^c = b
shg
²log3x = -3 ===> 3x = 2^(-3)
3x = 1/8
x = 1/24
²log3x = 1 ====> 3x = 2¹
x = 2/3
x yg memenuhi [1/24, 2/3]
2. ²log3 = a, ⁷log3 = b
³log2 = 1/a, ⁷log2 = ⁷log3.³log2
= b . 1/a = b/a
⁶log63 = ⁶log (21 . 3)
= ⁶log21 + ⁶log3
= ⁶log7 + ⁶log3 + ⁶log3
= 1/⁷log6 + 2. 1/³log6
= 1/[⁷log3 + ⁷log2] + 2/[³log3 + ³log2]
= 1/[b + b/a] + 2/[1 + 1/a]
= 1/[ba/a + b/a] + 2/[a/a + 1/a]
= a/(ab + b) + 2a/(a + 1)
= a/b(a + 1) + 2a/(a + 1)
= a/b(a + 1) + 2ab/b(a + 1)
= a(1 + 2b) / b(a + 1)
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