Question

(x-15)²=28

a resposta é
a: 15+-²√7

como chego na ²√7?

Answer 1

$\mathrm{(x-15)^2=28\ \to\ (x-15)^2=4.7\ \to}\\\\ \mathrm{\to\ x-15=\pm\sqrt{4.7}\ \to\ x-15=\pm\sqrt{4}\sqrt{7}\ \to}\\\\ \mathrm{\to\ x-15=\pm2\sqrt{7}\ \to\ x=\pm2\sqrt{7}+15\ \to}\\\\ \mathrm{\to\ \boxed{\mathbf{x=15\pm2\sqrt{7}}}}$