Question

Find the sum all even numbers form 2 to 40. By using formula find S_n = a = 2, d = 2, a_n = 40
a_n = find after S_n = find

Answer 1

$$\begin{gathered} Hi, \\ 2+4+6+...+40;itisAPwith \\ herea=2andcommondifferenced=2 \\ andlastterm=a+\left(n-1\right)d \\ 40=2+2\left(n-1\right) \\ 38=2n-2 \\ n=20 \\ sosum=\frac{n}{2}\left(first+lastterm\right) \\ =\frac{20}{2}\left(2+40\right) \\ =420 \end{gathered}$$