3.设函数$f(x)=\left\{ \begin{array}{cc} a{{x}^{2}}+b, \quad x\le 0, \\ \frac{{{\text{e}}^{ax}}-1}{x}, \quad x>0 \\ \end{array} \right.$在$x=0$处连续,则$a,\,\ b$满足关系式().
A. $a=b$
B. $a=-b$
C. $a=2b$
D. $a=-2b$
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4.设函数$y=y(x)$由$\left\{ \begin{matrix} x=a(t-\sin t), \\ y=a(1-\cos t) \\ \end{matrix} \right.$确定,则${y}''(x)=$().
A. $-\frac{1}{a(1-\cos t)}$
B. $-\frac{1}{a{{(1-\cos t)}^{2}}}$
C. $\frac{1}{a(1-\cos t)}$
D. $\frac{1}{a{{(1-\cos t)}^{2}}}$
5.设函数$y=y(x)$由方程${{(1+x)}^{{{y}^{2}}}}+{{y}^{2}}\ln x=2$确定,且$y(1)=1$,则${{\left. \text{d}y \right|}_{x=1}}=$().
A. $\frac{1}{2\ln 2}\text{d}x$
B. $-\frac{1}{2\ln 2}\text{d}x$
C. $\frac{3}{2\ln 2}\text{d}x$
D. $-\frac{3}{2\ln 2}\text{d}x$
2.当$x\to +\infty $时,曲线$y=\sqrt{{{x}^{2}}+x+1}$的渐近线方程为().
A. $y=x+\frac{1}{2}$
B. $y=x-\frac{1}{2}$
C. $y=2x+1$
D. $y=2x-1$
3.设函数$y=y(x)$由$\left\{ \begin{matrix} x=t+{{\text{e}}^{t}}, \\ y={{t}^{2}}+{{\text{e}}^{t}} \\ \end{matrix} \right.$确定,则曲线$y=y(x)$在点$(1,1)$处的切线方程为().
A. $y=\frac{1}{6}(x+5)$
B. $y=\frac{1}{4}(x+3)$
C. $y=\frac{1}{3}(x+2)$
D. $y=\frac{1}{2}(x+1)$