Question

answer this sum.....dont know don't amswer​

Answer 1

$\color{blue}{hope\:it\:helps}$

Answer 2

Question:

Find the sum of first 22 terms of the list of numbers whose nth term given by an = 3 + 2n..

Solution:

an = 3 + 2n

Let .. n = 1, 2, 3, 4,....

• a1 = 3 + 2(1)

→ 3 + 2 = 5

• a2 = 3 + 2(2)

→ 3 + 4 = 7

• a3 = 3 + 2(3)

→ 3 + 6 = 9

• a4 = 3 + 2(4)

→ 3 + 8 = 11

Now.. the AP is 5, 7, 9, 11, ....

Here..

First term (a) = 5

Common difference (d) = a2 - a1

→ 7 - 5 = 2

Number of terms (n) = 24

__________ [ GIVEN ]

• We have to find the first 22 terms of the list of the numbers.

_____________________________

We know that

» $S_{n}\:=\:\dfrac{n}{2}$ [2a + (n - 1)d]

Put the known values in above formula

→ $S_{24}\:=\:\dfrac{24}{2}$ [2(5) + (24 - 1)2]

→ $S_{24}$ = 12 [10 + 23(2)]

→ $S_{24}$ = 12(10 + 46)

→ $S_{24}$ = 12(56)

→ $S_{24}$ = 672

____________________________

672 is the first 22 terms of the list of the numbers whose nth term given by an = 3 + 2n..

________ [ ANSWER ]

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