Question

the nth term of an AP is given by an=3-5n

find the 8th term.
find the 21st term.
What is the first term?
deduce the common difference.

Answer 1

HERE IS YOUR ANSWER:

1) ✈$\underline{\textbf{8th term:}}$

a8= 3-5(8) = 3-40 = -37

2) ✈$\underline{\textbf{21st term:}}$

a21= 3-5(21) = 3- 105
= -102

3) ✈ $\underline{\textbf{first term}}$

a1 = 3-5(1) =-2

4) ✈$\underline{\textbf{common difference}}$

: a2-a1

a2 = 3-5(2) = 3-10 = -7

✈d= -7-(-2) = -7+2 = -5

:)

Answer 2

when n= 1
a1 = 3 - 5 × 1
= 3-5 = -2
when n = 2
a2 = 3-5×2
=3-10
-7
AP : -2, -7, -12,............
d = -7 +2
=-5
a = -2
a8 = 3-5 ×8
=3-40
=-37
a21 = 3-5×21
=3-105
-102