Sunday, May 24, 2015

Find the twentieth term of the arithmetic sequence with a1 = 15 and d = 4.

For an arithmetic progression we use the formula:

a%5Bn%5D=a%5B1%5D%2B%28n-1%29%2Ad

n=20, a1=15, d=4


a%5B20%5D=15%2B%2820-1%29%2A4

a%5B20%5D=15%2B19%2A4

a%5B20%5D=91

:)
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