“微信扫一扫”进入考试题库练习及模拟考试
第361题
若函数
参考答案:\(\sqrt 3 \)
第362题
函数
参考答案:\(\left[ {2, + \infty } \right)\)
参考答案:\(\left( { - \infty ,{e^{ - 2}}} \right]\)
参考答案:\(\frac{3}{2}\) 或 \(\frac{1}{2}\)
第365题
求
参考答案:\(f(x)\) 的定义域是 \(R\),令 \(y = \frac{{{2^x} - 1}}{{{2^x} + 1}}\),得\({2^x} = - \frac{{y + 1}}{{y - 1}}\)\(\because {2^x} > 0\),\(\therefore - \frac{{y + 1}}{{y - 1}} > 0\),解得 \( - 1 < y < 1\).\(\therefore f(x)\) 的值域为\(\left( { - 1,1} \right)\).
第366题
讨论
参考答案:\(\because f( - x) = \frac{{{2^{ - x}} - 1}}{{{2^{ - x}} + 1}} = \frac{{1 - {2^x}}}{{1 + {2^x}}} = - f(x)\),定义域为 \(R\),\(\therefore f(x)\) 是奇函数.
第367题
讨论
参考答案:\(f(x) = \frac{{\left( {{2^x} + 1} \right) - 2}}{{{2^x} + 1}} = 1 - \frac{2}{{{2^x} + 1}}\),设 \({x_1}\),\({x_2}\) 是 \(R\) 上任意两个实数,且 \({x_1} < {x_2}\),\(f({x_1}) - f({x_2}) = \frac{2}{{{2^{{x_2}}} + 1}} - \frac{2}{{{2^{{x_1}}} + 1}} = \frac{{2({2^{{x_1}}} - {2^{{x_2}}})}}{{({2^{{x_1}}} + 1)({2^{{x_2}}} + 1)}}\),\(\because {x_1} < {x_2}\),\(\therefore {2^{{x_2}}} > {2^{{x_1}}} > 0\),从而 \({2^{{x_1}}} + 1 > 0\),\({2^{{x_2}}} + 1 > 0\),\({2^{{x_1}}} - {2^{{x_2}}} < 0\),\(\therefore f({x_1}) - f({x_2}) < 0\),即\(f({x_1}) < f({x_2})\).\(\therefore f(x)\) 为 \(R\) 上的增函数.
A.\(f\left ( {c} \right )<f\left ( {b} \right )<f\left ( {a} \right )\)
B.\(f\left ( {b} \right )<f\left ( {c} \right )<f\left ( {a} \right )\)
C.\(f\left ( {b} \right )<f\left ( {a} \right )<f\left ( {c} \right )\)
D.\(f\left ( {a} \right )<f\left ( {b} \right )<f\left ( {c} \right )\)
参考答案:D
第369题
求
参考答案:由题意,\(f\left ( {0} \right )=k-1=0⇒k=1\),
代入验证,符合题意,
\(f\left ( {1} \right )=a-\frac {1} {a}=\frac {3} {2}⇒a=2\) 或\(a=-\frac {1} {2}\) (舍),
故\(k=1,a=2\) .
参考答案:令\(t={2}^{x}-{2}^{-x}\)
易知 \(t={2}^{x}-{2}^{-x}\) 为增函数,
故由\(x\in \left [ {-1,1} \right ]\) ,
可得:\(t\in \left [ {-\frac {3} {2},\frac {3} {2}} \right ]\)
对函数 \(g\left ( {x} \right )=h\left ( {t} \right )={t}^{2}-mt+2\),\(t\in \left [ {-\frac {3} {2},\frac {3} {2}} \right ]\)它的最小值为\(-2\)
等价于\(\left \{ \begin{gathered} {\frac {m} {2}<-\frac {3} {2}} \\ {h\left ( {-\frac {3} {2}} \right )=\frac {9} {4}+\frac {3} {2}m+2=-2} \end{gathered} \right .\) 或\(\left \{ \begin{gathered} {-\frac {3} {2}\leq \frac {m} {2}\leq \frac {3} {2}} \\ {h\left ( {\frac {m} {2}} \right )=\left ( {\frac {m} {2}} \right )^{2}-m\cdot \frac {m} {2}+2=-2} \end{gathered} \right .\) 或\(\left \{ \begin{gathered} {\frac {m} {2}>\frac {3} {2}} \\ {h\left ( {\frac {3} {2}} \right )=\frac {9} {4}-\frac {3} {2}m+2=-2} \end{gathered} \right .\) ,
解得:\(m=-\frac {25} {6}\) 或\(\frac {25} {6}\)
A.2
B.\(-2\)
C.1
D.\(-1\)
参考答案:C
A.\((-\infty ,-1]\)
B.\(\left ( {0,+\infty } \right )\)
C.\(\left ( {-1,0} \right )\)
D.\(\varnothing \)
参考答案:D
第373题
设指数函数
A.\(f\left( {x + y} \right) = f\left( x \right)f\left( y \right)\)
B.\(f\left( {x - y} \right) = \frac{{f\left( x \right)}}{{f\left( y \right)}}\)
C.\(f\left( {\frac{x}{y}} \right) = f\left( x \right) - f\left( y \right)\)
D.\(f\left( {nx} \right) = {\left[ {f\left( x \right)} \right]^n}\left( {x \in Q} \right)\)
参考答案:ABD
A.8
B.16
C.32
D.64
参考答案:D
第376题
已知函数
A.\(\left( {0,1} \right)\)
B.\(\left( { - 1,1} \right)\)
C.\(\left( { - 1,2} \right)\)
D.\(\left( {0,2} \right)\)
参考答案:C
第378题
与函数
A.\(y=x-1\)
B.\(y=\left | {x-1} \right |\)
C.\(y=\frac {{x}^{2}-1} {x+1}\)
D.\(y=\left ( {\frac {x-1} {\sqrt {x-1}}} \right )^{2}\)
参考答案:D
第379题
若
A.\(\frac {1} {4}\)
B.1
C.0
D.\(\frac {1} {2}e\)
参考答案:A
第380题
下列命题不正确的是( )
A.若 \(M = N\) ,则 \({\log -a}M = {\log -a}N\).
B.若 \({\log -a}M = {\log -a}N\) ,则 \(M = N\).
C.若 \({\log -a}{M^2} = {\log -a}{N^2}\) ,则 \(M = N\).
D.若 \(M = N\) ,则 \({\log -a}{M^2} = {\log -a}{N^2}\).
参考答案:ACD