Question

Se (4,9) é o ponto médio do segmento de extremos (2,y) e (x,3), qual o valor de x+y?:

a)9
b)-21
c)21
d)31​

Answer 1

$4=\dfrac{2+x}{2}\\2+x=8\\x=8-2=6$

$9=\dfrac{y+3}{2}\\y+3=18\\y=18-3=15$

$\boxed{\boxed{\mathsf{x+y=6+15=21}}}$

$\large\mathsf{Alternativa\,c}$