1.

Write the first five terms in each of the following sequences:(i) a1 = 1, an = an–1 + 2, n > 1(ii) a1 = 1 = a2, an = an–1 + an–2, n > 2(iii) a1 = a2 =2, an = an–1 – 1, n > 2

Answer»

(i) a1 = 1, an = an–1 + 2, n > 1

By using the values n = 1, 2, 3, 4, 5 we can find that the first five terms.

Given as

a1 = 1

Now, when n = 2:

a2 = a2–1 + 2

= a1 + 2

= 1 + 2

= 3

When n = 3:

a3 = a3–1 + 2

= a2 + 2

= 3 + 2

= 5

When n = 4:

a4 = a4–1 + 2

= a3 + 2

= 5 + 2

= 7

When n = 5:

a5 = a5–1 + 2

= a4 + 2

= 7 + 2

= 9

Thus, first five terms of the sequence are 1, 3, 5, 7, 9.

(ii) a1 = 1 = a2, an = an–1 + an–2, n > 2

By using the values n = 1, 2, 3, 4, 5 we can find the first five terms.

Given as

a1 = 1

a2 = 1

When n = 3:

a3 = a3–1 + a3–2

= a2 + a1

= 1 + 1

= 2

When n = 4:

a4 = a4–1 + a4–2

= a3 + a2

= 2 + 1

= 3

When n = 5:

a5 = a5–1 + a5–2

= a4 + a3

= 3 + 2

= 5

Thus, first five terms of the sequence are 1, 1, 2, 3, 5.

(iii) a1 = a2 =2, an = an–1 – 1, n > 2

By using the values n = 1, 2, 3, 4, 5 we can find the first five terms.

Given as

a1 = 2

a2 = 2

When n = 3:

a3 = a3–1 – 1

= a2 – 1

= 2 – 1

= 1

When n = 4:

a4 = a4–1 – 1

= a3 – 1

= 1 – 1

= 0

When n = 5:

a5 = a5–1 – 1

= a4 – 1

= 0 – 1

= -1

Thus, first five terms of the sequence are 2, 2, 1, 0, -1.



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