Answer: 18. B(5,-2) 19. C(4,10).
Step-by-step explanation:
18.
[tex]Let\ the\ midpoint\ of\ \overline {AB}\ is\ F\ and\ coordinates\ of \ B\ is\ (x,y).\\Hence,\\F_x=1\\\displaystyle\\F_x=\frac{A_x+B_x}{2} \\1=\frac{-3+x}{2} \\[/tex]
Multiply both sides of the equation by 2:
[tex]G_y=2.\\\displaystyle\\2=\frac{12+y}{2}[/tex]
[tex]4=6+y\\4-6=6-6+y\\-2=y.\\Hence, \ B(5,-2).[/tex]
19.
[tex]Let\ the\ midpoint\ of\ \overline {CD}\ is\ G\ and\ coordinates\ of \ C\ is\ (x,y).\\Hence,\\G_x=4\\\displaystyle\\G_x=\frac{C_x+D_x}{2} \\4=\frac{x+4}{2} \\[/tex]
Multiply both sides of the equation by 2:
[tex]8=x+4\\8-4=x+4-4\\4=x.[/tex]
[tex]G_y=11.\\\displaystyle\\11=\frac{y+12}{2}[/tex]
Multiply both sides of the equation by 2:
[tex]22=y+12\\22-12=y+12-12\\10=y.\\Hence, \ C(4,10).[/tex]
