Question

a, a+d, a+2d...l are n terms of an AP. find n-1th term of it in terms of 'l'.

Answer 1

L=a+(n-1)d ie a= L-(n-1)d
(n-1)th term = a+(n-2)d
                   = L-(n-1)d + (n-2)d
                   = L -dn +d +dn -2d
                   = L-d