Question

x=3+2root2 find the value of x square =81​

Answer 1

$x = 3 + 2 \sqrt{2} \\ {x}^{2} = {(3 + 2 \sqrt{2} )}^{2} \\ {x}^{2} = 9 + 8 + 12 \sqrt{2} \\ {x}^{2} = 17 + 12 \sqrt{2}$

$Since ,\: {x}^{2} = 81 \\ Therefore, \: x =± 9$