Question

find The 21st term of the A.P -4*1/2,-3,-1*1/2​

Answer 1

Answer:

Step-by-step explanation:

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Answer 2

21st term is $\bf \red{a_{21} = 25 \frac{1}{2} }$

Given:

• $- 4 \frac{1}{2}, \: - 3 ,\: - 1\frac{1}{2}, \: ...$

To find:

• Find the 21st term of the AP.

Solution:

Formula to be used:

General term of an AP: $\bf a_n = a + (n - 1)d$

here, a: first term

d: common difference

n: number of term

Step 1:

Write the first term and common difference of AP.

The given AP is

$- \frac{ 9}{2}, \: - 3 ,\: - \frac{3}{2},...$

Here

first term a:-9/2

Common difference d:

$- 3 - ( \frac{ -9 }{2} )$

or

$\frac{ - 6 + 9}{2}$

or

$\bf d = \frac{3}{2}$

and

n= 21

Step 2:

Find the 21th term of A.P.

$a_{21} = \frac{ -9 }{2} + (21 - 1) \frac{3}{2}$

or

$a_{21} = \frac{ -9 }{2} + 20 \times \frac{3}{2}$

or

$a_{21} = \frac{ -9 + 60 }{2}$

or

$\bf a_{21} = \frac{ 51 }{2}$

Thus,

$\bf a_{21} = 25 \frac{1}{2}$

Learn more:

1) 26th, 11th and last term of an ap are 0, 3 and -1/5 respectively . find the common difference and the number of terms

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2) for an AP the 12th term is 4 and the 20th term is -20. finf the nth term of the AP

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