Aptitude - Logarithm - Discussion
Discussion Forum : Logarithm - General Questions (Q.No. 5)
5.
| If log | a | + | log | b | = log (a + b), then: |
| b | a |
Answer: Option
Explanation:
| log | a | + log | b | = log (a + b) |
| b | a |
 log (a + b) = log |
 |
a | x | b |  |
= log 1. |
| b | a |
So, a + b = 1.
Discussion:
33 comments Page 1 of 4.
Md.anas said:
6 years ago
log(a/b)+log(b/a) = log(a+b)
log(a-b)+log(b-a) = log(a+b)
log(a-b)+log-(a-b) = log(a+b)
log(a-b)+log(1/a-b) = log(a+b)
log(a-b/a-b) = log(a+b)
log(1) = log(a+b)
1 = a+b
a+b = 1.
log(a-b)+log(b-a) = log(a+b)
log(a-b)+log-(a-b) = log(a+b)
log(a-b)+log(1/a-b) = log(a+b)
log(a-b/a-b) = log(a+b)
log(1) = log(a+b)
1 = a+b
a+b = 1.
(9)
Madhav said:
6 years ago
log(a/b) + log(b/a) = log(a+b).
>loga - logb + logb-loga = log(a+b),
>0 = log(a+b),
>log1 = log(a+b).
Therefore from LHS AND RHS.
a+b=1 ***log1 = 0.
>loga - logb + logb-loga = log(a+b),
>0 = log(a+b),
>log1 = log(a+b).
Therefore from LHS AND RHS.
a+b=1 ***log1 = 0.
(9)
Bhumika Bhawarkar said:
2 years ago
Excellent explanation. Thanks.
(5)
Archana said:
5 years ago
Thanks @Ragavendra.
(3)
Repith said:
5 years ago
Thank you very much for explaining this..
(3)
Pradeep Sharma said:
6 years ago
Here we have;
Log(a/b) + Log (b/a) = Log (a + b ) --> (1)
So, by taking LHS.
we have,
Log (a/b * b/a).
So, now we have Log 1 (as a/b * b/a =1).
From equation 1 we have;
Log 1 = Log (a+b).
So by this we have,
a+b =1.
Hence proved.
Log(a/b) + Log (b/a) = Log (a + b ) --> (1)
So, by taking LHS.
we have,
Log (a/b * b/a).
So, now we have Log 1 (as a/b * b/a =1).
From equation 1 we have;
Log 1 = Log (a+b).
So by this we have,
a+b =1.
Hence proved.
(2)
Kevin augustine said:
7 years ago
Log a/b + log b/a = log(a+b).
Then,
log a - log b + log b - log a = log (a + b).
Lhs cancelled each other so lhs = 0.
Then,
log (a + b) = 0.
So a+b should be 1.
Answer is 1.
Then,
log a - log b + log b - log a = log (a + b).
Lhs cancelled each other so lhs = 0.
Then,
log (a + b) = 0.
So a+b should be 1.
Answer is 1.
(1)
Patil said:
6 years ago
I cannot understand please explain the method in detail.
Siddharth said:
9 years ago
I have a question.
Log a =log b
a = b
a * a = ab
(a * a)- b * b = ab - b *b
(a + b)(a - b) = b(a - b)
a + b = b
But a = b
So
B + b = b
Were is the mistake? Please clarify this.
Log a =log b
a = b
a * a = ab
(a * a)- b * b = ab - b *b
(a + b)(a - b) = b(a - b)
a + b = b
But a = b
So
B + b = b
Were is the mistake? Please clarify this.
Shubham said:
7 years ago
Thanks all for giving the solution.
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