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========== Suppose you add up one plus two plus four
plus eight plus sixteen plus… well, youget the point. Each number is twice as big
as the previous one, so it's pretty obviousthat this sum is infinite…But wait a second! We can multiply the whole
thing by one and it'll be the same, right?And one is the same as two minus one… so
we have two plus four plus eight plus sixteenetc., minus one minus two minus four minus
eight minus sixteen…So almost everything on the right side cancels,
and voila: 1+2+4+8+16, and so on, is negativeone!