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I will prove that 1=0.999999... This one
IS NOT a troll (no sneaky tricks like the last one i.e. dividing by zero).
The Fractions Proof
This one requires little to no math knowledge. Note that
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One third is equal to 0.33333...
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Three times one third is equal to 1:
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Three times 0.33333... is equal to 0.999999...
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Therefore 1=0.999999...
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The Infinite Series Proof
A number with a repeating decimal can be represented as a sum of an infinite series:
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The formula to find the value of an infinite series where |r|<1 is as follows:
S is the sum, t1 is the first term in the series, and r is the rate.
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Therefore:
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The Algebraic Proof
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Multiply both sides by 10 (remember that when you multiply by ten it shifts the decimal place to the right by one place):
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Subtract x=0.9999... from both sides:
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Simplify:
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Divide by 9:
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The Midpoint Proof
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What is the midpoint (average) between a and b? The formula to find m where m is the midpoint is:
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Using the values for a and b:
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You can use long division to divide 1.9999... by 2 to get m=0.99999...
Since the midpoint between the two points IS one of the two points, the two points MUST be equal. If you are unconvinced that this is true, you could say from the information that:
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Multiply both sides by two:
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Subtract b from both sides:
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Simplify:
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Substituting numerical values:
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