Question

pls help me ......................

Answer 1

7.
$(a + \frac{1}{a})^{2} = a^{2} + { (\frac{1}{a} )}^{2} + 2 \times a \times \frac{1}{a} \\ = a^{2} + { (\frac{1}{a} )}^{2} + 2$

8.
$(x + \frac{1}{x} ) = 25 \\Squaring\ both\ the\ sides \\ {(x + \frac{1}{x} ) }^{2} = {25}^{2} = 625 \\ {x}^{2} + { (\frac{1}{x} )}^{2} + 2 = 625 \\ {x}^{2} + { (\frac{1}{x} )}^{2} = 625 - 2 \\ {x}^{2} + \frac{1}{ {x}^{2} } = 623$