![](data:image/svg+xml;utf8,<svg xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" viewBox="0 0 72 71" width="72"></svg>)
19+199+1999+...+19999...999
Original formula = 20 + 200 + 200 +... + 200... 00-n
N is the number of zeros
222222…… 220-n
13+14+15+16+17+…… +26+27=
13+27=40 14+26=40 15+25=40.
If you count 13 to 27, there are 15 numbers in total, except that the number in the middle is 20, and the rest are exactly 7 40s
That adds up to 300
7 out of 18 times 2 out of 25 plus 2 out of 17 plus 9 out of 25
7/18×2/25=14/450
18 × 25 as denominator and 7 × 2 as numerator
14/450+2/17+9/25
Denominator Division
238/7650+900/7605+2754/7650
The molecules are added and then simplified
13 + (- 12) + 17 + (- 18)
Original formula = 13-12 + 17-18
=1+17-18
=0
That's it
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