Question

a,b,c,l,m are in A.P then the value of a-4b+6c-4l+m is

Answer 1

since a, b, c ,l ,m are in A.P.
a + m = 2c .......................(1)
b + l = 2c ..................(2)
a - 4b + 6c - 4l + m
= a + m + 6c - 4(b+l)
= 2c + 6c - 8c 
= 0                         

Answer 2

a-4b+6c-4l+m
=(a+m)-4(b+l)+6c     (2c=b+l,a+m=b+l=2c)
=2c-4(2c)+6c
=2c-8c+6c
=0