SOLUTION: please help me with this mathematical induction 1/2^1+1/2^2+1/2^3+....+1/2^n =1-1/2^n.

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Question 1141231: please help me with this mathematical induction 1/2^1+1/2^2+1/2^3+....+1/2^n =1-1/2^n.
Answer by math_helper(2461) About Me  (Show Source):
You can put this solution on YOUR website!
please help me with this mathematical induction 1/2^1+1/2^2+1/2^3+....+1/2^n =1-1/2^n.
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please help me by proving this statement using mathematical induction 1%2F2%5E1%2B1%2F2%5E2%2B1%2F2%5E3+ + ... + +1%2F2%5En+=+1-1%2F2%5En.


n=1: +1%2F2%5E1+=+1%2F2+=+1-1%2F2%5E1+ Ok for n=1. This is the base-case.
Assume it is true for n=k: that is, +1%2F2%5E1+%2B+1%2F2%5E2+ + ... + +1%2F2%5En+ = +1-1%2F2%5En+ holds for n=k. This is the hypothesis statement.
Now look at the case n=k+1:
+1%2F2%5E1+%2B+1%2F2%5E2+ + ... + +1%2F2%5Ek+%2B+1%2F2%5E%28k%2B1%29+
If we exclude the very last term for a second, the remainder is the same case as n=k, which we can re-write by applying the hypothesis:
= +1+-+1%2F2%5Ek+ + +1%2F2%5E%28k%2B1%29+
Putting everthing over a common denominator (step-by-step):
=
= +%282%5E%28k%2B1%29+-+2+%2B+1%29+%2F+2%5E%28k%2B1%29+
= +%282%5E%28k%2B1%29+-+1%29+%2F+2%5E%28k%2B1%29+
Dividing the numerator by the denominator:
= +1+-+%281%2F2%5E%28k%2B1%29%29+ DONE (the hypothesis leads to truth for n=k+1)