Answer:
(5, 24)
Step-by-step explanation:
In order to find the midpoint of a line, you need two sets of coordinates. The formula to find the midpoint of a line is [tex](\frac{x1+x2}{2} ,\frac{y1+y2}{2} )[/tex], where [tex]x1[/tex] is the x-coordinate of one of the coordinates and [tex]x2[/tex] is the x-coordinate of the second coordinate (and so on for [tex]y1[/tex] and [tex]y2[/tex]).
In this question, we're not given the two sets of coordinates to find the midpoint from. But we are told there is an interval 1 < x < 9, so first we substitute x=1 into the equation of the line: [tex]y=3[/tex]×[tex]1+9[/tex] = 3 + 9 = 12. So one of the coordinates is (1, 12). Doing the same with x=9, will give us y = 24.
Now if we use the formula I've written above, we should get (5, 24).
