Question

What is the 87th term of the arithmetic sequence?

Answer 1

Step-by-step explanation:

1) The first term is -1352, and the common difference is 18.  So the 87th term is:

a = -1352 + 18 (87 − 1)

a = 196

2) 1/64 + 1/16 + 1/4 + 1 + 4

This is a geometric series, where the first term is 1/64 and the common ratio is 4.

∑⁵ᵢ₌₁ 1/64 (4)ⁱ⁻¹

Since 1/64 = 4⁻³:

∑⁵ᵢ₌₁ 4⁻³ (4)ⁱ⁻¹

∑⁵ᵢ₌₁ (4)ⁱ⁻⁴

3) The first term is -2100, and the common ratio is -0.1, so the 7th term is:

a = -2100 (-0.1)⁷⁻¹

a = -0.0021

4) The first term is 48, and the fifth term is 243/16, so the common ratio is:

243/16 = 48 r⁵⁻¹

81/256 = r⁴

r = 3/4

So the sequence is:

48, 36, 27, 81/4, 243/16