The sum of the first 20 terms is 670, and the 20th term is 62. As this is an arithmetic sequence, we know the difference between each term will be *d. u *is the term, *n *is the number of term.

a) What is the first term, u_{1}?S_{n}= n/2 x (u_{1}+u_{n})S_{20} = n/2 x (u_{1}+u_{20}) = 20/2 x (u_{1}+ 62) 670 = 10 x (62 + u_{1}) = 620 + 10u_{1}(670 - 620) = 10u_{1}50 = 10u_{1}, u_{1} = 5

b) What is the common difference, d?u_{n}= u_{1}+(n-1)*d*u_{20}= u_{1}+19*d*62 = 5 + 19d57 = 19dd = 3

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