Answer:
im in 8th grade and im getting your questions
Step-by-step explanation:
Answer:
S
ThenSn=n(a1+an)2Sn=n(a1 + an)2 , where nn is the number of terms, a1a1 is the first term and anan is the last term. The sum of the first nn terms of an arithmetic sequence is called an arithmetic series .
Step-by-step explanation:
twice the sum of a number and 3, means you need to add the number to 3 first, then multiply by 2.
The correct expression would be 2(n+3)