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Find the 7th term of the arithmetic sequence -5x-8,-x-14,3x-20,...

1 Answer

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a₁ = -5x-8; a₂ = -x-14; a₇=?

d = a₂ - a₁
= x-14 - (-5x-8)
= -x - 14 + 5x + 8
= 4x-6

a(n) = a₁ + (n-1)d

a₇ = -5x-8 + (7-1)(4x-6)
= -5x-8 + 6(4x-6)
= -5x - 8 + 24x - 36
= 19x - 44
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