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高中数学必修 第一册(648题)






第365题



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



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



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.


第368题


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



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\(k=1,a=2\) .


第370题



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\(\frac {25} {6}\)




第373题


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


第374题

指数函数 \(y = f(x)\) 经过点 \(( - 2,\frac{1}{4})\) ,那么 \(f\left( 4 \right)f\left( 2 \right) = \) (  )


A.8

B.16

C.32

D.64


参考答案:D



第376题


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


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


A.\(\frac {1} {4}\)

B.1

C.0

D.\(\frac {1} {2}e\)


参考答案:A


第380题


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


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