Question

7. Se (7, 11) é o ponto médio do segmento de extremos (15, y) e (x, 23), determine x+y. *
a) -2
b) 0
c) -10
d) 20

Answer 1

$\boxed{\begin{array}{l}\sf M(7,11)\\\sf A(x,23)~~B(15,y)\\\sf x_M=\dfrac{x_A+x_B}{2}\longrightarrow x_A+x_B=2 x_M\\\sf x+15=2\cdot7\\\sf x+15=14\\\sf x=14-15\\\sf x=-1\\\sf y_M=\dfrac{y_A+y_B}{2}\longrightarrow y_A+y_B=2y_M\\\sf 23+y=2\cdot11\\\sf 23+y=22\\\sf y=22-23\\\sf y=-1\\\sf x+y=-1-1=-2\\\huge\boxed{\boxed{\boxed{\boxed{\sf\red{\maltese}~\blue{alternativa~a} }}}}\end{array}}$