Question

Line AB has endpoints A(-4,5) and B(3,5). What is the x-coordinate of a point C such that B is the midpoint of line AC

Answer 1

easy peasy

the midpoint between
`(x_1,y_1)` and
`(x_2,y_2)` is

`((x_1+x_2)/(2),(y_1+y_2)/(2))`
just average them

so given that (3,5) is the midpoint of (-4,5) and (x,y)

`((-4+x)/(2),(5+y)/(2))=(3,5)`
so by logic

`(-4+x)/(2)=3` and
`(5+y)/(2)=5`
times both sides by 2 for everybody
-4+x=6 and 5+y=10
add 4 to both sides for left one and minus 5 from both sides for right
x=10 and y=5

the coordinate of point C is (10,5)
the x coordinate is 10