Question

(3 + x)² + (3-x)² = 36.​

Answer 1

$\boxed{(a+b)^2=a^2+2ab+b^2}\\\boxed{(a-b)^2=a^2-2ab+b^2}$

$(3+x)^2+(3-x)^2=36\\9+6x+x^2+9-6x+x^2=36\\2x^2=36-18\\x^2=\frac{18}{2} \\x^2=9\implies \boxed{ x=\pm 3}$