What is the 25th term of the arithmetic sequence where a1 = 8 and a9 = 48?

2 Answers
Jul 9, 2018

a_25=128a25=128

Explanation:

We know that ,

color(blue)(n^(th)term " of the arithmetic sequence is :"nthterm of the arithmetic sequence is :

color(blue)(a_n=a_1+(n-1)d...to(I)

We have ,

color(red)(a_1=8 and a_9=48

Using (I) ,we get

=>a_9=a_1+(9-1)d=48

=>8+8d=48

=>8d=48-8=40

=>color(red)(d=5

Again using (I) ,we get

a_25=a_1+(25-1)d

=>a_25=8+24(5)

=>a_25=128

Jul 9, 2018

a_(25)=128

Explanation:

"the n th term of an arithmetic sequence is"

•color(white)(x)a_n=a_1+(n-1)d

"where d is the common difference"

"given "a_1=8" then"

a_9=8+8d=48rArr8d=40rArrd=5

a_(25)=8+(24xx5)=128