Computer Sciences > GATE 2024 SET-2 > Logarithm
For positive non-zero real variables x and y, if ln((x+y)/2)=1/2[ln(x)+ln(y)], then , the value of x/y+y/x
A
1/2
B
1
C
2
D
4

Correct : c

Explanation:
Let us simplify the given logarithmic equation step-by-step using standard logarithm rules.
1. Apply Logarithmic Properties:
The given equation is:
    ln((x + y) / 2) = 1/2 [ln(x) + ln(y)]

Using the log addition rule, ln(x) + ln(y) = ln(xy):
    ln((x + y) / 2) = 1/2 ln(xy)

Using the power rule, b · ln(a) = ln(ab):
    ln((x + y) / 2) = ln((xy)1/2)

2. Remove the Natural Logarithm from Both Sides:
    (x + y) / 2 = √(xy)
    x + y = 2√(xy)

3. Square Both Sides to Eliminate the Radical:
    (x + y)2 = (2√(xy))2
    x2 + 2xy + y2 = 4xy

Bring 4xy to the left side:
    x2 - 2xy + y2 = 0
    (x - y)2 = 0
    x - y = 0 → x = y

4. Evaluate the Target Expression:
Since x = y, we substitute y for x (or vice versa) in the expression x/y + y/x:
    x/y + y/x = y/y + y/y = 1 + 1 = 2

5. Conclusion:
The value of the expression is exactly 2, making option (c) the correct choice.

Similar Questions

A palindrome is a word that reads the same forwards and backwards. In a game of words, a player has the following two plates painted with letters. From...
#1 MCQ
Which number does not belong in the series below? 2, 5, 10, 17, 26, 37, 50, 64
#4 MCQ
Choose the word that is opposite in meaning to the word “coherent”.
#5 MCQ

Related Topics

No tags found

Unique Visitor Count

Total Unique Visitors

Loading......