[tex] \sqrt{ ({ \frac{1 + a}{1 - a} })^{x} } = 1 + ax + \frac{1}{2} {a}^{2} {x}^{2} + \frac{x}{b} ( { {x}^{2} + 2 })^{3} [/tex]
If a is so small that it's fourth and higher powers can be neglected then show that if
[tex]x = 1[/tex]
and
[tex]a = \frac{1}{4} [/tex]
, prove that
[tex] \sqrt{15 } [/tex]
≈
[tex]3 \times \frac{111}{128} [/tex]
​