# Aptitude - Logarithm - Discussion

Discussion Forum : Logarithm - General Questions (Q.No. 9)

9.

If log

_{10}5 + log_{10}(5*x*+ 1) = log_{10}(*x*+ 5) + 1, then*x*is equal to:Answer: Option

Explanation:

log_{10} 5 + log_{10} (5*x* + 1) = log_{10} (*x* + 5) + 1

log_{10} 5 + log_{10} (5*x* + 1) = log_{10} (*x* + 5) + log_{10} 10

log_{10} [5 (5*x* + 1)] = log_{10} [10(*x* + 5)]

5(5*x* + 1) = 10(*x* + 5)

5*x* + 1 = 2*x* + 10

3*x* = 9

*x* = 3.

Discussion:

14 comments Page 1 of 2.
Gilbert Langat said:
2 years ago

@All.

According to me;

Log 5(4t+7) - log5t = 2.

According to me;

Log 5(4t+7) - log5t = 2.

Vijju said:
4 years ago

@Chi.

How log 10 10 = 1?

How log 10 10 = 1?

Chi said:
4 years ago

One of the laws of the log is log10 10=1

log2 2=1

log5 5=1

logx x=1

@Saim.

Log 2 to the power 2 (written as log 2^2) = 2*Log2 and not 1.

log2 2=1

log5 5=1

logx x=1

@Saim.

Log 2 to the power 2 (written as log 2^2) = 2*Log2 and not 1.

Victor said:
4 years ago

@Saim.

We can't replace it with log2^2 because log2^2 =2log2 not 1.

We can't replace it with log2^2 because log2^2 =2log2 not 1.

Devota said:
4 years ago

I'm not getting this, please anyone explain in detail.

Biswa said:
5 years ago

I want to all formula & explanation about logarithms?

Saim said:
6 years ago

It's solved wrongly. Because log2^2 or log4^4 is also equal to 1. If we put these in replace of one the answer is wrong.

Correct me, if I am wrong.

Correct me, if I am wrong.

Ashmi said:
7 years ago

How logx x=1?

Sharmi said:
7 years ago

Logx x =1 (it's one of the property).

So, log10 10=1.

Inorder to find x, 1 is being replaced with log10 10.

So, log10 10=1.

Inorder to find x, 1 is being replaced with log10 10.

Bhavya said:
7 years ago

Log10 10=1 so place of1 they take log10 10.

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