Sums (without Solutions)

These sums were taken from the book Number Theory by George E. Andrews

What is the equation for each of the following sums that gives the sum for a given $n$:

(1)  $1 + 2 + 3 + \dots + n$

(2)  $1^2 + 2^2 + 3^2 + \dots + n^2$

(3)  $1^3 + 2^3 + 3^3 + \dots + n^3$

(4)  $1 + x + x^2 + x^3 + \dots + x^n$

(5)  $1\times2 + 2\times3 + 3\times4 + \dots + (n)(n+1)$

(6)  $1 + 3 + 5 + \dots + (2n-1)$

(7)  $\dfrac{1}{1\times2} + \dfrac{1}{2\times3} + \dfrac{1}{3\times4} + \dots + \dfrac{1}{n(n+1)}$