共50条信息
若\(\dfrac{1}{a}{ < }\dfrac{1}{b}{ < }0\),则下列不等式:\({①}\dfrac{1}{a{+}b}{ < }\dfrac{1}{{ab}}\);\({②}{|}a{|} + b{ > }0\);\({③}a{-}\dfrac{1}{a}{ > }b{-}\dfrac{1}{b}\);\({④}{\ \ln }a^{2}{ > }\ln b^{2}\)中,不正确的不等式是\({\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ }({ }{\ \ \ \ \ \ }{ })\)
B.
\((1)\)已知\(x > 1\),求证:\({{x}^{2}}+\dfrac{1}{{{x}^{2}}} > x+\dfrac{1}{x}\);
\((2)\)已知\(x∈R\),\(a=x^{2}-x+1\),\(b=4-x\),\(c=x^{2}-2x.\)试用反证法证明\(a\),\(b\),\(c\)中至少有一个不小于\(1\).
已知\(1\leqslant a\leqslant 3\),\(-4 < b < 2\),则\(a+|b|\)的取值范围是________.
设\(a=\int _{1}^{2} \dfrac{1}{x}dx,b=\int _{1}^{3} \dfrac{1}{x}dx,c=\int _{1}^{5} \dfrac{1}{x}dx \),则下列关系式成立的是\((\) \()\)
\((2)\)若\(x∈\left(0,1\right) \)时不等式\(f\left(x\right) > x \)成立,求\(a\)的取值范围.
设\(a={{\log }_{0.2}}0.3\),\(b={{\log }_{2}}0.3\),则\((\) \()\)
\((2)\)若\(f(-\dfrac{3}{2}) < 3\),求实数\(a\)的取值范围.
已知\(0 < a < \)\( \dfrac{1}{2}\),\(A=1-a\)\({\,\!}^{2}\),\(B=1+a\)\({\,\!}^{2}\),\(C=\)\( \dfrac{1}{1-a}\),\(D=\)\( \dfrac{1}{1+a}\),试比较\(A\),\(B\),\(C\),\(D\)的大小.
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