The 7th term of an ap is 40 the sum of its first 13th term is a)5oo. b)51o. c)52o. d)53o​

520

Step-by-step explanation:

40=a+6d

a=40-6d

S13=13/2(2(40-6d)+12d)

S13=13/2(80-0)

S13= 13/2(80)

=520

Let the first term be a and common difference is d,

a+(7−1)d=40

a+6d=40

Now sum of 13 term is

13/2(2a + 12d)= 13/2*2*40=520

okk

byyyyy

Step-by-step explanation:

This is ur answer dude hope u like it

• Let the first term of an A.P. be a and common difference is d. So the 7th term of the A.P. is 40=> a+6d =40.

Sum of first 13 terms = 13/2(a +(a+12d))= 13/2(2a+12d) =

13/2(2)(a+6d) =13(a+6d) =13(40)=

520 .

• 7th term = 40

• Sum of the first 13th term = ?

Let us assume that the first term be a and the common difference be d.

We know that,

Now,

Therefore, sum of the first 13th term is 520.

• The general form of an AP is

• Formula to find the nth term of an AP is

where,

• Formula to find the numbers of term of an AP is

where,

Firstly, we know that formula an A.P;

Where as;

A/q

Now, using formula of the sum of an A.P;

Thus;

The sum of first 13th term is 520 .