Toán 7

B

braga

[TEX]f(x)=x^2+x+1=x^2+\frac{1}{2}x+\frac{1}{2}x+\frac{1}{4}+\frac{3}{4} \\\\ = x\left ( x+\frac{1}{2} \right )+\frac{1}{2}\left ( x+\frac{1}{2} \right )+\frac{3}{4} \\\\ = \left ( x+\frac{1}{2} \right )\left ( x+\frac{1}{2} \right) +\frac{3}{4}=\left ( x+\frac{1}{2} \right )^2+\frac{3}{4}\geq \frac{3}{4}[/TEX]

Với mọi x ta luôn có [TEX]f(x) \not= 0[/TEX]. Vậy f(x) không có nghiệm
 
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