Question

Find the sum of m terms of an A.P., a - 3d, a -
2d, a-d, a, a + d, a + 2d + .....​

Answer 1

Answer:

according to the formula,

the sum of n terms of a.p= n/2(2a +(n-1)d)

here,

sum of m terms of a.p =m/2{ 2(a-3d) + (m-1)d}

=m/2{2a -6d +md -d}

=m/2{2a -7d +md }

=m/2{2a +(m-7)d}

hence

the sum of m terms of a.p =m/2{2a+(m-7)d} answer