Question

If the nth term of an ap is given by an=5n-3 then the sum of first 10 terms is .

Answer 1

Answer:

a1=5×1-3=2

a10=5×10-3

sum of 10 terms = n/2(a1+an)

=10/2(2+47)=245

pls follow

Answer 2

The sum of first 10 terms is 245.

Step-by-step explanation:

Given : The nth term of A.P is  $a_n=5n-3$

To find : The sum of first 10 terms ?

Solution :

The nth term of A.P is  $a_n=5n-3$

Put n=1,

$a_1=5(1)-3$

$a_1=2$

The first term is 2.

Put n=2,

$a_2=5(2)-3$

$a_2=7$

The common difference is $d=a_2-a_1$

$d=7-2$

$d=5$

The sum of n term is given by,

$S_n=\frac{n}{2}(2a+(n-1)d)$

$S_{10}=\frac{10}{2}(2(2)+(10-1)5)$

$S_{10}=5(4+(9)5)$

$S_{10}=5(4+45)$

$S_{10}=5(49)$

$S_{10}=245$

Therefore, the sum of first 10 terms is 245.

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