Question

Guys! Need an answer, got a test tomorrow....​

Answer 1

$x + y = 20 \\ xy = 20 \\ (x + y) {}^{2} = 20 {}^{2} \\ {x}^{2} + {y}^{2} + 2xy = 400 \\ {x}^{2} + {y}^{2} + 2(20) = 400 \: \: \: (put \: xy \: = 20) \\ {x}^{2} + y {}^{2} + 40 = 400 \\ {x}^{2} + y {}^{2} = 400 - 40 \\ {x}^{2} + {y}^{2} = 360$

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