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Question
If a = log 20 b = log 25 and 2 log (p - 4) = 2a - b, find the value of 'p'.
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Solution
a = log 20, b = log 25 and 2 log (p - 4) = 2a - b
⇒ 2 log (p - 4) = 2a - b
⇒ 2 log (p - 4) = 2log20 - log25
⇒ log (p - 4)2 = log202 - log25
⇒ log (p - 4)2 = `"log"(400/25)`
⇒ (p - 4)2 = `(400)/(25)`
⇒ p2 - 8p + 16 = 16
⇒ p2 - 8p = 0
⇒ p(p - 8) = 0
⇒ p = 0 or p = 8.
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