Q). Solve for x: \frac{1}{x + 1} + \frac{3}{5 x + 1} = \frac{5}{x + 4}, x ≠ 1, – \frac{1}{5}, – 4

Ans:

\frac{1}{x + 1} + \frac{3}{5 x + 1} = \frac{5}{x + 4}

\frac{1 (5 x + 1) + 3 (x + 1)}{(x + 1)(5 x + 1)} = \frac{5}{x + 4}

\frac{5 x + 1 + 3 x + 3}{(x + 1)(5 x + 1)} = \frac{5}{x + 4}

\frac{8 x + 4}{(x + 1)(5 x + 1)} = \frac{5}{x + 4}

∴ (8 x + 4) (x + 4) = 5 (x + 1)(5 x + 1)

∴ 8 x2 + 4 x + 32 x + 16 = 5 ( 5 x2 + 5 x + x + 1)

∴ 8 x2 + 36 x + 16 = 25 x 2 + 25 x + 5 x + 5

∴ 17 x2 – 6 x – 11 = 0

∴ 17 x2 – 17 x + 11 x – 11 = 0         (by mid term splitting)

∴ 17 x (x – 1) + 11 (x – 1) = 0

∴ (x -1) (17 x + 11) = 0

Hence we get x = 1 and x = \frac{- 11}{17}

Here we reject x = 1 (because it is given that x ≠ 1); and select x = \frac{- 11}{17}

Therefore, value of x = \frac{- 11}{17}.

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