toán lớp 8(đại số)???

H

harrypham

Ta có [TEX]\left( x^2- \frac{1}{x^2} \right): \left( x^2+ \frac{1}{x^2} \right)=a[/TEX]
[TEX]\Rightarrow \frac{x^4-1}{x^2}: \frac{x^4+1}{x^2}=a \Rightarrow a= \frac{x^4-1}{x^4+1}[/TEX]
[TEX]\Rightarrow x^4-1=ax^4+a \Rightarrow x^4= \frac{a+1}{1-a}[/TEX].
Do đó [TEX]M= \left( x^4- \frac{1}{x^4} \right): \left( x^4+ \frac{1}{x^4} \right)[/TEX]
[TEX]= \left( \frac{a+1}{1-a}- \frac{1-a}{a+1} \right): \left( \frac{a+1}{1-a}+ \frac{1-a}{a+1} \right) = \frac{4a}{(a+1)(1-a)}: \frac{2a^2+2}{(a+1)(1-a)}[/TEX]
[TEX]= \fbox{\frac{2a}{a^2+1}}[/TEX]
 
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