the 40th term of an arithmetic sequence is equal to the sum of the 20th and 31st term. if the common difference of the sequence is-10. find the first term.
2 answers
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"the 40th term of an arithmetic sequence is equal to the sum of the 20th and 31st term"
----> a + 39d = a+19d + a+30d
a = -10d
but d = -10
a = 100
the first term is 100
----> a + 39d = a+19d + a+30d
a = -10d
but d = -10
a = 100
the first term is 100