Question

5 - (FGV-SP) Sabendo que x² + y² = 13 e que xy = 6, dê o valor de (x + y)²
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Answer 1

(x+y).(x+y)=x²+xy+xy+y²
x²+y²+2xy, xy=6
x²+y²+2.6
x²+y²+12, x²+y²=13
13+12=25