Question

Find an equation for the nth term of the arithmetic sequence.
a19 = -92, a20 = 6

an = -1856 + 98(n - 1)
an = -1856 - 98(n - 1)
an = -1856 - 98(n + 1)
an = -1856 + 98(n + 1)

Answer 1

an=a₁+(n-1)*d Formula for nth term
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a19 = -92

-92 = a₁ + 18*d

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a20 = 6

6 = a₁ + 19*d
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Solve these two equations for d and a₁

-92 = a₁ + 18*d
6 = a₁ + 19*d
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Answer 2

im confused

Answer 3

@Directrix

Answer 4

Add the second equation from the first (the ones on the right side) so that you can solve for d which is the common difference of the terms in the sequence.

-92 = a₁ + 18*d ---> -92 = a₁ + 18*d
6 = a₁ + 19*d -- (-1)--> -6 = - a₁ -19*d
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