If x ≥ y and y > 1, then the value of the expression
logxxy+logyyx can never be
Explanation:
logxxy+logyyx = logx x - logx y + logy y - logy x
⇒ logxxy+logyyx = 1 - logx y + 1 - logy x
⇒ logxxy+logyyx = 2 - logx y - logy x
⇒ logxxy+logyyx = 2 - (logx y + logy x)
As x ≥ y and y > 1, logy x ≥ 0 Now, (logx y + logy x) = logxy+1logxy [This is sum of a positive number and its reciprocal]
Now, sum of a positive number and its reciprocal is always greater than or equal to 2.
∴ (logx y + logy x) = logxxy+logyyx ≥ 2
⇒ logxxy+logyyx = 2 - (logx y + logy x) ≤ 0
∴ logxxy+logyyx ≠ 1
Hence, option (d).
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