Write the codding for summation of this series

Question

1+4+7+10+……..n

1*2+2*3+3*4+4*5+…….+n*(n+1)

20+22+24+……+30

Answer 1

For all 3 of these, we can take advantage of Matlab's vector functionality:

For the first, since the step is constantly 3, we can make the vector (assuming n is defined)

v = 1:3:n

Then the series is simply

sum(v)

For the second, we will actually use two vectors and a dot product. The two vectors are

v1 = 1:n and

v2 = 2:(n+1)

Then the summation is the inner product of the two 

v1*v2' 

For the third, we will do almost the same as the first, but with different values.

v = 20:2:30

So that the sum is

sum(v)