Question

An arithmetic sequence has a common difference of 5 and the 3rd term is 15. What is the 5th term?

Answer 1

Answer:

an=8n−14

Step-by-step explanation:

for an AP

where

a

1

=

the first term

d

=

the common difference

then we have

a

1

,

(

a

1

+

d

)

,

(

a

1

+

2

d

)

,

...

,

a

1

+

(

(

n

−

1

)

d

)

,

.

.

we are given the third term

10

=

a

1

+

2

d

−

−

(

1

)

and the fifth term

26

=

a

1

+

4

d

−

−

(

2

)

subtract

(

2

)

−

(

1

)

16

=

2

d

⇒

d

=

8

sub into

(

1

)

10

=

a

1

+

2

×

8

⇒

a

1

=

−

6

so the nth term

a

n

=

a

+

(

n

−

1

)

will be

a

n

=

−

6

+

8

(

n

−

1

)

a

n

=

8

n

−

14