Question

What numbers form a right triangle

Answer 1

let's recal the pythagorean theorem, where c² = a² + b², namely, the largest number squared is equal to the sum of the two smaller ones squared.

well, we can just start by say in A, looking the smaller sides, 3 and √9, if we squared both and add them up, do they give the largest one of √18?

$\boxed{A} \\\\ 3^2+(\sqrt{9})^2 = (\sqrt{18})^2\implies 9+9 =18\qquad \textit{\Large\checkmark} \\\\\\ \boxed{B}\\\\ 3^2+4^2=5^2\implies 9+16=25\implies 25=25\qquad \textit{\Large\checkmark} \\\\\\ \boxed{C}\\\\ 7^2+7^2=(\sqrt{98})^2\implies 49+49=98\implies 98=98\qquad \textit{\Large\checkmark}$

so they all apply.