7. Find the sum of the first 20 terms of the sequence. Paper size | Letter Print 5, 14, 23, 32, ... S20 = 8. Find 1 + 2+3+4+ ... +80, the sum of the first 80 natural numbers. The sum is 9. Write out the first three terms and the last term. Then use the formula for the sum of the first n terms of an arithmetic sequence to find the indicated sum. (41 -3) 1 =1 a, = a2 ag The last term is a21 = The partial sum of the first 21 terms is $21 = 10. Company A pays $24,000 yearly with raises of $1,400 per year. Company B pays $28,500 yearly with raises of $800 per year. Which company will pay more in year 10? How much more? Which company pays more in year 10? O Both companies pay the same . O Company A pays more. O Company B pays more. O There is not enough information. How much more