Question

resposta da equacao x+y=7 xy=12​(preciso urgente )

Answer 1

Resposta:

x=3 e y=4 ou x=4 e y=3

Explicação passo-a-passo:

x+y=7

xy=12 =>y=12/x

Substituindo y=12/x em x+y=7:

x+y=7

x+12/x=7

x²+12=7x

x²-7x+12=0

$Aplicando~a~f\'{o}rmula~de~Bhaskara~para~x^{2}-7x+12=0~~\\e~comparando~com~(a)x^{2}+(b)x+(c)=0,~temos~a=1{;}~b=-7~e~c=12\\\\\Delta=(b)^{2}-4(a)(c)=(-7)^{2}-4(1)(12)=49-(48)=1\\\\x^{'}=\frac{-(b)-\sqrt{\Delta}}{2(a)}=\frac{-(-7)-\sqrt{1}}{2(1)}=\frac{7-1}{2}=\frac{6}{2}=3\\\\x^{''}=\frac{-(b)+\sqrt{\Delta}}{2(a)}=\frac{-(-7)+\sqrt{1}}{2(1)}=\frac{7+1}{2}=\frac{8}{2}=4\\\\S=\{3,~4\}$

Para x=3

y=12/x=12/3=4

Para x=4

y=12/x=12/4=3