2.下列关于x的方程中,一定有实数根的是( )
| A. | $\sqrt{x}$+1=0 | B. | $\sqrt{x}$=-x | C. | $\sqrt{{x}^{2}+3}$=0 | D. | $\frac{x}{x-1}$=$\frac{1}{x-1}$ |
20.
如图,在平面直角坐标系xOy中,菱形ABCD的顶点A(3,0)和B(0,4),则图象过点C的反比例函数解析式为( )
| A. | $y=\frac{20}{x}$ | B. | $y=-\frac{20}{x}$ | C. | $y=\frac{12}{x}$ | D. | $y=-\frac{12}{x}$ |
16.
将正方形纸片ABCD按如图所示对折,使边AD与BC重合,折痕为EF,连接AE,将AE折叠到AB上,折痕为AH,则$\frac{BH}{BC}$的值是$\frac{\sqrt{5}-1}{2}$.
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