[Toán 8] Tính giá trị biểu thức

V

vinhthanh1998

Ta có: [TEX]x+\frac{1}{x}=2007[/TEX]
[TEX]\Rightarrow (x+\frac{1}{x})^2=2007^2=4028049[/TEX]
[TEX]\Rightarrow x^2+2+\frac{1}{x^2}=4028049[/TEX]
[TEX]\Rightarrow x^2+\frac{1}{x^2}=4028049-2[/TEX]
[TEX]\Rightarrow x^2+\frac{1}{x^2}=4028047[/TEX]
Vậy: [TEX]A=x^3+\frac{1}{x^3}[/TEX]
[TEX]A=x^3+(\frac{1}{x})^3[/TEX]
[TEX]A=(x+\frac{1}{x})(x^2-1+\frac{1}{x^2})[/TEX]
[TEX]A=2007.4028046[/TEX]

[TEX]A=8084288322[/TEX]
 
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