Question

A²+9\a²=31 then find (a-3/a)²

Answer 1

$= > a {}^{2} + \frac{9}{a {}^{2} } = 31\\ = > a {}^{2} + ( \frac{3}{a} ) {}^{2} = 31 \\ \\ now \: \: \: \: ......... \\ (a - \frac{3}{a} ) {}^{2} = a {}^{2} + ( \frac{3}{a} ) {}^{2} - 2 \times a \times \frac{3}{a} \\ \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: = 31 - 6 = 25 \\ = > (a - \frac{3}{a} ) {}^{2} = 25$