Question

Write the 1st, 2nd, 3rdand 18thterms for: A) Un= n2 + 4 B) Un = 6n + 5

Answer 1

Answer:

(a) $U_1 =5$; $U_2 = 8$; $U_{18} = 328$

(b) $U_1 = 11$; $U_2 =17$; $U_{18} = 113$

Step-by-step explanation:

Required

1st, 2nd and 18th terms

To do this, we simply substitute 1, 2 or 18 for n in the given equations

Solving (a):

$U_n =n^2 + 4$

1st term: n = 1

$U_1 =1^2 + 4$

$U_1 =1 + 4$

$U_1 =5$

2nd term: n = 2

$U_2 = 2^2 + 4$

$U_2 = 4 + 4$

$U_2 = 8$

18th term: n = 18

$U_{18} = 18^2 + 4$

$U_{18} = 324 + 4$

$U_{18} = 328$

Solving (b):

$U_n = 6n + 5$

1st term: n = 1

$U_1 = 6*1 + 5$

$U_1 = 6 + 5$

$U_1 = 11$

2nd term: n = 2

$U_2 = 6*2 + 5$

$U_2 =12 + 5$

$U_2 =17$

18th term: n = 18

$U_{18} = 6*18 + 5$

$U_{18} = 108 + 5$

$U_{18} = 113$