Question

Find the value of 'a' ,for which P(a/2,2) is the midpoint of the line segment joining the points Q(-5,4) and R(-1,0).

Answer 1

(a/2,2)=[{-5+(-1)}/2,( 4+0)/2]. using midpoint formula.
so a/2=-6/2
a=-6

Answer 2

p(a/2,2)
Q(-5,4)
R(-1,0)
as P is the midpoint
so,
slope of PQ = slope of PR
2-4/a/2+5 = 2-0/a/2+1
-2/a+10/2 = 2/a+2/2
-2*2/a+10 = 2*2/a+2
-4/a+10 = 4/a+2
-4(a+2) = 4(a+10)
-4a - 8 = 4a + 10
4a+4a = -40-8
8a = -48
a= -48/8 = -6