수학 채널

(n+1)^2=n^2+2n+1

->(n+1)^2-n(2n+1)=-n^2-n=n^2-n(2n+1)

->(n+1)^2-n(2n+1)+(2n+1)^2/4=n^2-n(2n+1)+(2n+1)^2/4

->((n+1)-(2n+1)/2)^2=(n-(2n+1)/2)^2

->n+1-(2n+1)/2=n-(2n+1)/2

->n+1=n

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