Math, asked by Killer9996, 1 year ago

find the 21st term of an AP = - 9/2,-3,-3/2​

Answers

Answered by sharonr
4

The 21st term is 51/2

Solution:

Given that,

The arithmetic sequence is:

\frac{-9}{2}, -3, \frac{-3}{2}

Find the common difference between a term and its previous term

d = -3-(\frac{-9}{2})\\\\d = -3+\frac{9}{2}\\\\d = \frac{-6+9}{2}\\\\d = \frac{3}{2}

The nth term in an AP is given as:

a_n = a_1 + (n-1)d

Where,

n is the nth term

d is the common difference

a_1 is the first term

Find the 21st term:

Substitute

n = 21\\\\d = \frac{3}{2}\\\\a_1 = \frac{-9}{2}

Therefore,

a_{21} = \frac{-9}{2} + (21-1) \times \frac{3}{2}\\\\a_{21} = \frac{-9}{2} + 20 \times \frac{3}{2}\\\\\a_{21} =  \frac{-9}{2} + 30\\\\a_{21} =  \frac{-9+60}{2}\\\\a_{21} =  \frac{51}{2}

Thus 21st term is found

Learn more about AP

Sum of three consecutive terms of an Arithmetic Progression is 42 and their product is 2520.  Find the terms of the Arithmetic Progression.

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Which term of the Arithmetic Progression - 7,-12,-17,-22 will be -82 ? Is -100 any term of the A.P. ? Give reason for your answer.

https://brainly.in/question/8619006

Answered by musarrtjahan2000
0

Answer:

a= -9/2

d=3/2

n=21

d= b-a

b=-3-(-9/2)

=3/2

an =a+(n-1)d

put the givens in this equation

will be

an= -9/2+(21-1)3/2

an=-9/2+(20)3/2

an= -9/2+60/2

an= 51/2

step

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