Question

Evaluate the arithmetic series. Please help me!!!

Answer 1

Explanation:

∑1 to 18 (5n-4)

a1=5×1-4=1

a2=5×2-4=6

a18=5×18-4=86

n=18

`S_(n)=(n)/(2) (a1+an)\\S_(18)=(18)/(2) (1+86)=9 * 87=783`