Find : 1-2+3-4+5-6+......+17-18+19-20
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Answered by
37
Hi ,
1 -2 + 3 - 4 + .....+ 19 - 20
= ( 1+3+5+.….+19)-( 2+4+6+.…+20 )
= 10² - [ 10/2 ( 2 + 20 ) ]
= 100 - ( 10 × 11 )
= 100 - 110
= -10
Or
( 1-2) + (3 - 4 )+ ( 5 - 6 ) +...+ ( 19 - 20 )
= -1 -1 -1 -....10 times
= 10 × ( -1 )
= -10
I hope this helps you.
: )
1 -2 + 3 - 4 + .....+ 19 - 20
= ( 1+3+5+.….+19)-( 2+4+6+.…+20 )
= 10² - [ 10/2 ( 2 + 20 ) ]
= 100 - ( 10 × 11 )
= 100 - 110
= -10
Or
( 1-2) + (3 - 4 )+ ( 5 - 6 ) +...+ ( 19 - 20 )
= -1 -1 -1 -....10 times
= 10 × ( -1 )
= -10
I hope this helps you.
: )
Answered by
20
Hi,
Please see the attached file!
Thanks
Please see the attached file!
Thanks
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