make a conjecture about the sum of the first 30 positive even numbers.
2
=
1 · 22 + 4
6
2 · 32 + 4 + 6
12
3 · 42 + 4 + 6 + 8
20
4 · 52 + 4 + 6 + 8 + 10
30
5 · 6
To find 30n we use formula
Sn=n/2⋅(2a1+(n−1)⋅d)
In this example we have a1=2 , d=2 , n=30. After substituting these values into the above equation, we
obtain:
S30 = 930
i hope this helped,
gavin
