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TV BQT tích cực 2017
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$A=\dfrac1{1-x}+\dfrac1{1+x}+\dfrac2{1+x^2}+\dfrac 4{1+x^4}+\dfrac 8{1+x^8}+\dfrac{16}{1+x^{16}}
\\=\dfrac{1+x+1-x}{1-x^2}+\dfrac2{1+x^2}+\dfrac 4{1+x^4}+\dfrac 8{1+x^8}+\dfrac{16}{1+x^{16}}
\\=\dfrac 2{1-x^2}+\dfrac2{1+x^2}+\dfrac 4{1+x^4}+\dfrac 8{1+x^8}+\dfrac{16}{1+x^{16}}
\\=\dfrac{2+2x^2+2-2x^2}{1-x^4}+\dfrac 4{1+x^4}+\dfrac 8{1+x^8}+\dfrac{16}{1+x^{16}}
\\=\dfrac{4}{1-x^4}+\dfrac 4{1+x^4}+\dfrac 8{1+x^8}+\dfrac{16}{1+x^{16}}
\\=\dfrac{4+4x^4+4-4x^4}{1-x^8}+\dfrac 8{1+x^8}+\dfrac{16}{1+x^{16}}
\\=\dfrac{8}{1-x^8}+\dfrac 8{1+x^8}+\dfrac{16}{1+x^{16}}
\\=\dfrac{8+8x^8+8-8x^8}{1-x^{16}}+\dfrac{16}{1+x^{16}}
\\=\dfrac{16}{1-x^{16}}+\dfrac{16}{1+x^{16}}
\\=\dfrac{16+16x^{16}+16-16x^{16}}{1-x^{32}}
\\=\dfrac{32}{1-x^{32}}$
 
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