Question

A sequence is given by the formula un=3n+5 for n=1,2,3... Write down the first five terms of this sequence

Answer 1

Answer:

Your answer is:-

Step-by-step explanation:

A sequence is given by the formula un = 3n + 5, for n = 1, 2, 3. What are the first five terms of this sequence?

un=3n+5 for n=1,2,3

un=3×n+5=8n

Five terms n=1,2,3,4,5

u1=3×1+5=8

u2=3×2+5=11

u3=3×3+5=14

u4=3×4+5=17

u5=3×5+5=20

First five terms are 8,11,14,17,20

Given nth term:

un = 3n+5 —-(1)

Method 1:

u1 = 3(1)+5 = 8; u2 = 3(2)+5 = 11 ; u3 = 3(3)+5 = 14

Similarly, u4 = 17 and u5 = 20

First 5 terms are: 8, 11, 14, 17, 20

Method 2:

For an AP with first term = and common difference = d, n th term is given by,

tn = a+(n-1)d

tn = a+dn - d

Comparing with eqn. (1),

d= 3 ; a-d = 5 ⇒ a= 5+5 = 8

First 5 terms are: 8, 11, 14, 17, 20