Question

If a =5-2 under root 5,then find a²

Answer 1

Step-by-step explanation:

$a = 5 - 2 \sqrt{5} \\ {a}^{2} = {(5 - 2 \sqrt{5}) }^{2} \\ {a}^{2} = {(5)}^{2} + {(2 \sqrt{5}) }^{2} - 2(5)(2 \sqrt{5}) \\ {a}^{2} = 25 + 20 - 20 \sqrt{5} \\ {a}^{2} = 45 - 20 \sqrt{5}$