If log7 log5 x+5+x = 0, find the value of x.
Explanation:
log7 log5 x+5+x = 0
We know
loga b = x ⇒ ax = b
∴log5 x+5+x = 70 ⇒ log5x+5+x = 1 ⇒ x+5+x = 51 ⇒ x+5=5-x
Squaring both sides ⇒ x + 5 = 25 + x − 2 × 5x ⇒ x + 5 = 25 + x + 10x
⇒ 10x = 20 ⇒ x = 2 ⇒ x2 = (2)2 ⇒ x = 4
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