AAG Arithmetic Sequences

Question

Common difference: -2

Fourth Term: 1

What is the 10th term?

And

Fifth term: 6

Eleventh term: 36

What are the first 4 terms?

Answer 1

a₄ = a₁ + 3d; a₁ = a₄ - 3d = 1 + 6 = 7; a₁₀ = a₁ + 9d = 7 - 18 = - 11

a₅ = a₁ + 4d = 6, a₁₁ = a₁ + 10d = 36, from here 6d = 30, d = 5; a₁ = - 14; so, 1st 4 terms: -14, - 9, - 4, 1.

Answer 2

a4=1

d = -2

a4 = a1 -2(3) = 1

a1 = 1+6=7

a10 = 7 -2(9) = -11= 10th term

a5 = 6

a11 = 36

d = (36-6)/(11-5) = 30/6 = 5

a5 =a1 +5(4)=6

a1 = 6-20= -14

a2 = -9

a3 = -4

a4 = 1

1st 4 terms are -14,-9,-4, 1