(a+b)(a²+b²)(a^4+b^4)(a^8+b^8)...(a^2n+b^2n).=
(a - b) · (a+b)(a²+b²)(a^4+b^4)(a^8+b^8)...(a^2n+b^2n). · 1 / ( a -b)
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( a² - b² ) ·
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( a^4 - b^4 ) ·
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= ( a^4n - b^4n ) / ( a - b)
b)Fie A=(1+1supra a)(1+1supra a^2)(1+1supra a^4)...(1supra a^2n)
( 1 - 1 / a ) ·(1+1/a)(1+1/ a^2)(1+1/ a^4)...(1+1/ a^2n) · a / ( a +1) =
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= ( 1 - 1 /a² )
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= [ 1 - 1 / (a^4n) ] · a / ( a +1)