Question

se x+y=13 e xy=13, então x2+y2 é?

Answer 1

x+y=13⇒(x+y)²=13²⇒x²+2xy+y²=169⇒x²+2·13+y²=169 ⇒x²+26+y²=169⇒
x²+y²=169-26⇒x²+y²=143