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Solve for x if \(25^{x} + 3(5^{x}) = 4\)

Mathematics
JAMB 1994

Solve for x if \(25^{x} + 3(5^{x}) = 4\)

  • A. 1 or -4
  • B. 0
  • C. 1
  • D. -4 or 0
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Correct Answer: Option B
Explanation

\(25^{x} + 3(5^{x}) = 4\)

Let \(5^{x}\) = y.

\((5^{2})^{x} + 3(5^{x}) - 4 = 0\)

\(y^{2} + 3y - 4 = 0\)

\(y^{2} - y + 4y - 4 = 0\)

\(y(y - 1) + 4(y - 1) = 0\)

\((y + 4)(y - 1) = 0\)

\(y = -4 ; y = 1\)

y = -4 is not possible.

y = 1 \(\implies\) x = 0.


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