Question

resolva x² + y²=41 e x+y=9

Answer 1

$x=9-y\\\\x^2+y^2=41\\\\(9-y)^2+y^2=41\\\\81-18y+y^2+y^2=41\\\\2y^2-18y+81-41=0\\\\2y^2-18y+40=0\\\\y^2-9y+20=0\\\\\Delta=81-80=1\\\\y=\dfrac{9\pm1}{2}\\\\y=5\ ou\ y=4\\\\x+5=9\\\\x=4\\\\x+4=9\\\\x=5\\\\\boxed{S:\{(4,5),(5,4)\}}$