Question

if a, b, c, l,m are in ap to a-4b+4bc-4l+m+l=?​

Answer 1

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