Question

Find the sum. 0+3+6+...+(3n-3)

Answer 1

Explanation:

a1 = 0

an = a1 + (n -1)*d = 3n - 3

a1 = 0

(n - 1)*d = 3(n-1)

From which d = 3

Now for the sum

Sum = (a1 + an)*n/2

Sum = (an * n)/2

Sum = 3(n - 1) * n / 2

Sum = (3n - 3)*n/2

Sum = (3n^2 - 3n)/2