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If \(1 - \log_{10}2 = \log_{10}(5^x + 4^x + 3^x + 2^x + 1)\), then what is a value of x ?

This question was previously asked in
NDA 2 2026 GAT Question Paper (13-Sep-2026)
The correct answer is
0

Solving the Logarithmic Equation

We are asked to find the value of \(x\) in the equation: \(1 - \log_{10}2 = \log_{10}(5^x + 4^x + 3^x + 2^x + 1)\)

Simplifying the Left Side

First, simplify the term \(1 - \log_{10}2\). We know that \(1 = \log_{10}10\). Using the logarithm property \(\log_b M - \log_b N = \log_b (M/N)\), we get:

\(1 - \log_{10}2 = \log_{10}10 - \log_{10}2 = \log_{10}\left(\frac{10}{2}\right) = \log_{10}5\)

Equating Logarithm Arguments

Now, substitute the simplified term back into the original equation:

\(\log_{10}5 = \log_{10}(5^x + 4^x + 3^x + 2^x + 1)\)

Since the logarithms have the same base (base 10), their arguments must be equal:

\(5 = 5^x + 4^x + 3^x + 2^x + 1\)

Finding the Value of x

We need to find the value of \(x\) that satisfies \(5^x + 4^x + 3^x + 2^x + 1 = 5\). Let's test the value \(x=0\) (Option D):

If \(x = 0\), then:

\(5^0 + 4^0 + 3^0 + 2^0 + 1 = 1 + 1 + 1 + 1 + 1 = 5\)

Since substituting \(x=0\) satisfies the equation, \(x=0\) is the correct value.

Final Answer Check

The equation simplifies to \(5 = 5^x + 4^x + 3^x + 2^x + 1\). Testing \(x=0\) gives 1+1+1+1+1 = 5, which is true. Therefore, the value of \(x\) is 0.

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