Question

i challenge you to answer in 4 minutes for 50 points

if x=7+√40 find x^2-1/x^2

Answer 1

Answer in attachment. Answer is 4√5+2√2/3. Please comment if you need detailed explanation. Try to solve such problems by yourself in the future. :)

Answer 2

${(7 + \sqrt{40} )}^{2} - 1 \div {(7 + 40)}^{2} \\ 49 + 40 + 14 \sqrt{40} - 1 \div 49 + 40 + 14 \sqrt{40} \\ 88 + 14 \sqrt{40} \div 89 + 14 \sqrt{40}$
$0.994 \: approx$