Question

Determine the sum : 1+ (-2) + 3 + (-4) +5+ (-6) + .... + (-50).
I​

Answer 1

Answer:

⇒ 1 - 2 + 3 - 4 + 5 - 6 .... - 50   ( 50 terms)

⇒ (1 - 2) + (3 - 4) + (5 - 6) ....+ (49 - 50)  ( 25 terms)

⇒ (-1) + (-1) + (-1) + (-1) + .... + (-1)   (25 terms)

⇒ -1 × 25 = -25

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By using formula,

⇒ 1 - 2 + 3 - 4 + 5 - 6 .... - 50

⇒ ( 1 + 3 + 5 + 7 + ... + 49 ) - ( 2 + 4 + 6 + 8 + ... + 50 )

applying

a=1 a1=2

n=25

d=2

in

sn=n/2(2a+(n-1)d)

=-25

Step-by-step explanation:

Answer 2

Answer:

-25

There are 25 pairs.

Answer of one pair is -1.

Then 25*-1=-25

Thanks.