Question

what is the sum of (a-d)+(a+d)
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Answer 1

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ANSWER

In series a,a+d,a+2d..........a+2nd

The first term =a , common difference=d

Term =2n+1

Last term =a+2nd

We know that sum of series

=

2

2n+1

(fist term+last term)

=

2

2n+1

(a+a+2nd)=(2n+1)(a+nd)

Then mean of series

=

2n+1

sum of series

=

n

(2n+1)(a+nd)

=(a+nd)

Answer 2

2a

Explanation:

a - d + a + d

=>a + a + d - d

= 2a + 0

= 2a

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