Question

if x+y=9 x-y=7 ,find xy​

Answer 1

sorry mate do not know the answer ............

Answer 2

Answer:

$xy = \frac{(x + y) {}^{2} }{2} - \frac{(x - y) {}^{} }{2}^{2} \\ xy = \frac{(9) {}^{2} }{2} - \frac{(7) {}^{2} }{2} \\ xy = \frac{81}{2} - \frac{49}{2} \\ xy = 40.5 - 24.5 \\ xy = 16$

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