Question

please answer with step by step explanation ​

Answer 1

$\sqrt{2 {x}^{2} + 9 } = 9 \\ 2 {x}^{2} + 9 = 81 \\ 2 {x}^{2} - 72 = 0 \\ 2( {x}^{2} - 36) = 0 \\ {x}^{2} - 36 = 0 \\ {x}^{2} = 36 \\ x = + 6 \\ x = - 6 \\ \\ hope \: thi s \: answer \: helps \: plz \: mark \: as \: brainliest$