Assuming \(|x|\) to be so small, that \(x^2\) and higher powers of \(x\) can be neglected, then…

Assuming \(|x|\) to be so small, that \(x^2\) and higher powers of \(x\) can be neglected, then \(\frac{\sqrt{1+x}+(1-x)^{3 / 2}}{(1+x)+\sqrt{1+x}}=\)
  1. \(1+\frac{5 x}{4}\)
  2. \(1-\frac{5 x}{4}\)
  3. \(1+\frac{4 x}{5}\)
  4. \(1-\frac{4 x}{5}\)

Solution

Given, \(|x|\) is very small, \(x^2\) is negligible \(\begin{aligned} & \frac{\sqrt{1+x}+(1-x)^{3 / 2}}{(1+x)+\sqrt{1+x}}=\frac{1+\frac{1}{2} x+1-\frac{3}{2} x}{1+x+1+\frac{x}{2}} \\ & =\frac{2-x}{2+\frac{3 x}{2}}=\frac{4-2 x}{4+3 x}=\frac{(4-2 x)(4-3 x)}{\left(16-9 x^2\right)} \\ & =\frac{16-20 x+6 x^2}{16-9 x^2}=\frac{16-20 x}{16}\left\{\because x^2 \text { negligible }\right\} \\ & =1-\frac{5 x}{4} \end{aligned}\)

Asked in: AP EAMCET 2020 (17 Sep Shift 1)

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