x 1 2 3 4 5
y 2 6 12 20 30
1 times 1 more than 1, or 2, is 2
2 times 1 more than 2, or 3, is 6
3 times 1 more than 3, or 4, is 12
4 times 1 more than 4, or 5, is 20
5 times 1 more than 5, or 6, is 30
So
x times 1 more than x, or x+1, is y
So x(x+1) = y
or y = x(x+1)
Edwin