Question

12. Si x2 +y 2 =82; x+y=10. Calcular xy

Answer 1

$\left \{ {{x^2+y^2=82} \atop {x+y=10}} \right. \\ \\ \left \{ {{x^2+y^2=82} \atop {y=10-x}} \right. \\ \\ Reemplazamos \\ \\ x^2+(10-x)^2= 82 \\ \\ x^2+100-20x+x^2= 82 \\ \\ 2x^2-20x+100-82=0 \\ \\ 2x^2-20x+18= 0 \\ \\ 2*(x-9)*(x-1) =0 \\ \\ x_1=+9\qquad x_2= +1$



Espero que te sirva, salu2!!!!