InterviewSolution
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`1/2+1/4+1/8+1/16+.......+1/2^n=1-1/2^n` |
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Answer» `" Let "P(n) : 1/2+1/4+1/8+.........+1/2^(n)=1-1/2^(n)` for n=1 `L.H.S. =1/2` `R.H.S. =1-1/2^(1)` `=1-1/2=1/2` `:. " "L.H.S. =R.H.S.` therefore P (n) is true for n=1. Let P (n) true for n=k `P (n) : 1/2+1/4+1/8+......+1/2^(k) =1-1/2^(k)` for n=K+1 `P(k+1) : 1/2+1/4+1/8+......+1/2^(k)+1/2^(k+1) =1-1/2^(k)+1/2^(k+1)` `=1-((1)/(2^(k))-(1)/(2^(k+1)))` `=1-((2-1)/(2^(k+1)))=1-(1)/(2^(K+1))` `rArr` P (n) is also true for n=K+1 Hence from the principle of mathematical induction the given statement is true for all natural numbers n. |
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