Find the value of x for which 6\(\sqrt{4x^2 + 1}\) = 13x, where x >

FURTHER MATHEMATICS
WAEC 2019

Find the value of x for which 6\(\sqrt{4x^2 + 1}\) = 13x, where x > 0

  • A. \(\frac{6}{5}\)
  • B. \(\frac{25}{24}\)
  • C. \(\frac{24}{25}\)
  • D. \(\frac{5}{6}\)

Correct Answer: A. \(\frac{6}{5}\)

Explanation

\(\sqrt{4x^2 + 1}\) = \(\frac{13x}{6}\)

4x\(^2\) + 1 = \(\frac{169x^2}{36}\)

4 + x\(^2\) = \(\frac{169x^2}{36}\)

cross multiply

169x\(^2\) - 144x\(^2\) = 36

25x\(^2\) = 36

x\(^2\) = \(\frac{36}{25}\)

: x = \(\pm\frac{6}{5}\)



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