Geometry And Algebra Formulas
Midpoint Formula…3 problems; algebra?
We never learned these in algebra, but they are on my algebra review sheet for geometry… Please show all your steps, so I can understand what you’re doing. Help me! Please and thank you 
Midpoint formula: If A and B are endpoints and M is a midpoint, find each missing item:
A(8, -7) B(-2, 11) M = ?
A (m, n) B (t, r) M = ?
A (3, -6) M = (12, -6) B = ?
I have no idea how to do these…my algebra teacher skipped over this lesson 
Thank you!!
@ i’m with stupid: this is great! i am so happy someone answered my question, and actually helped! this is not as hard as i thought it would be. i know how to do it now, ALL thanks to YOU. thank you sooooooo much!
think of the midpoint as being the average of the endpoints:
so
midpoint of (m, n) and (p, q)
is the average abscissa: (m+p)/2
and the average ordinate: (n+q)/2
so the midpoint is:
((m+p)/2, (n+q)/2)
given
A = (8, -7) and B = (-2, 11)
average abscissa: (8 + -2)/2 = 3
average ordinate: (-7 + 11)/2 = 2
so:
M = (3, 2)
given
A = (m, n) and B = (t, r)
M = ((m+t)/2, (n+r)/2)
given
A = (3, -6) and M = (12, -6)
then
12 = (3+p)/2, so p = 21 ← abscissa
-6 = (-6+q)/2, so q = -6 ← ordinate
and
B = (21, -6)
♣♦
1-5 Using Formulas in Geometry
