Expand (9−2x)12\displaystyle (9-2x)^{\frac{1}{2}}(9−2x)21 in ascending powers of x x\,x up to and including x3x^3x3
Write down the range of values of x x\,x for which the expansion is valid.
Use your expansion, with a suitable value of xxx, to find the value of 8.9 \sqrt{8.9}\,8.9 correct to 5 significant figures