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Answers ( 37 )
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    Jim should receive 3/8 of the proceeds.

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    Slice the number XII = 12 across the middle to get VII = 7.

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    In base 2, 1 + 1 = 10

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    Where is "d"?

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    We have: \(y^2=x\left(x+1\right)\left(x+2\right)\left(x+3\right)\)

               \(\Leftrightarrow y^2+1=x\left(x+1\right)\left(x+2\right)\left(x+3\right)+1\)

               \(\Leftrightarrow y^2+1=\left(x^2+3x+1\right)^2\)

    \(\Rightarrow y=0\) (Because \(y^2\) and \(\left(x^2+3x+1\right)^2\) is two consecutive square numbers)

    \(\Rightarrow\left[{}\begin{matrix}x=0\\x+1=0\\x+2=0\\x+3=0\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}x=0\\x=-1\\x=-2\\x=-3\end{matrix}\right.\)

    So x=0; x=-1; x=-2; x=-3.

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    When n has three digits, we have:

          \(n+S\left(n\right)\le999+27=1026\) (!)

    \(\Rightarrow\) n has four digits.

    Now we have: 

           \(\left(1000a+100b+10c+d\right)+\left(a+b+c+d\right)=1982\)

      \(\Leftrightarrow1001a+101b+11c+2d=1982\) (1)

    \(\Rightarrow a=\left[\dfrac{1982}{1001}\right]=1\)

    \(\left(1\right)\Leftrightarrow101b+11c+2d=981\) (2)

    \(\Rightarrow b=\left[\dfrac{981}{101}\right]=9\)

     \(\left(2\right)\Leftrightarrow11c+2d=72\) (3)

    \(\Rightarrow c=\left[\dfrac{72}{11}\right]=6\)

     \(\left(3\right)\Leftrightarrow2d=6\Leftrightarrow d=3\)

    Because the factoring is only one 

    So a=1; b=9; c=6; d=3.

          

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    Condition: \(x\ge82\)

    We have: \(\sqrt{x+7}-\sqrt{x-82}=x-2017\)

              \(\Leftrightarrow\left(\sqrt{x+7}-45\right)+\left(44-\sqrt{x-82}\right)+2018-x=0\)

              \(\Leftrightarrow\dfrac{x-2018}{\sqrt{x+7}+45}+\dfrac{2018-x}{\sqrt{x-82}+44}+2018-x=0\)

              \(\Leftrightarrow\left(2018-x\right)\left(\dfrac{1}{\sqrt{x-82}+44}-\dfrac{1}{\sqrt{x+7}+45}+1\right)=0\)

    \(x\ge82\Rightarrow1>\dfrac{1}{\sqrt{x+7}+45}>\dfrac{1}{\sqrt{x-82}+44}>0\Rightarrow\dfrac{1}{\sqrt{x-82}+44}+1-\dfrac{1}{\sqrt{x+7}+45}>0\)

    \(\Rightarrow2018-x=0\Rightarrow x=2018\)

    So \(x=2018\).

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    abc is different 0 \(\Rightarrow\) a, b, c is different 0.

    We have: \(\dfrac{x-b-c}{a}+\dfrac{x-a-c}{b}+\dfrac{x-a-b}{c}=3\)

              \(\Leftrightarrow\left(\dfrac{x-b-c}{a}-1\right)+\left(\dfrac{x-a-c}{b}-1\right)+\left(\dfrac{x-a-b}{c}-1\right)=0\)

              \(\Leftrightarrow\dfrac{x-a-b-c}{a}+\dfrac{x-a-b-c}{b}+\dfrac{x-a-b-c}{c}=0\)

              \(\Leftrightarrow\left(x-a-b-c\right)\left(\dfrac{1}{a}+\dfrac{1}{b}+\dfrac{1}{c}\right)=0\)

              \(\Leftrightarrow x-a-b-c=0\) (because \(\dfrac{1}{a}+\dfrac{1}{b}+\dfrac{1}{c}\ne0\))

              \(\Leftrightarrow x=a+b+c\)

    So \(x=a+b+c\)

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    We have: \(P=10a^2+10b^2+c^2\)

                        \(=\left(8a^2+\dfrac{1}{2}c^2\right)+\left(8b^2+\dfrac{1}{2}c^2\right)+\left(2a^2+2b^2\right)\)

                        \(\ge2\sqrt{8a^2.\dfrac{1}{2}c^2}+2\sqrt{8b^2.\dfrac{1}{2}c^2}+4\sqrt{a^2b^2}\) (AM-GM inequality)

                        \(=4ac+4bc+4ab\)

                        \(=4\left(ab+bc+ca\right)=4\)

    So the minimum of P is 4 when \(a=b=\dfrac{1}{3};c=\dfrac{4}{3}\).

                        

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    \(1000000!:999999!=\left(1.2.3.....1000000\right):\left(1.2.3.....999999\right)=1000000\)

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    We have: \(x^2\) is a square number

    \(\Rightarrow x\in Z\)

    -C1: \(x⋮3\)

    \(\Rightarrow x^2\equiv0\) (mod 3)

    \(\Rightarrow x^2+5\equiv2\) (mod 3) (Impossible because \(x^2+5\) is a square number)

    -C2: \(x⋮̸3\)

    \(\Rightarrow x^2\equiv1\) (mod 3)

    \(\Rightarrow x^2-5\equiv2\) (mod 3) (Impossible because \(x^2-5\) is a square number)

     So can't find x.

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    \(\sqrt{2.3.4.5.6.7.10}=\sqrt{50400}=60\sqrt{14}\)

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    \(5-5.5+5:5=5-25+1=-19\)

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    1: \(12.37+12.7+12.6\)

      \(=444+84+72\)

      \(=600\)

    2: \(12.37+12.7+12.6\)

     \(=12\left(37+7+6\right)\)

     \(=12.50\)

     \(=600\).

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    We have: \(y^2=\left(y+2018\right)^2\)

             \(\Leftrightarrow\left(y+2018\right)^2-y^2=0\)

             \(\Leftrightarrow2018\left(2y+2018\right)=0\)

             \(\Leftrightarrow2y=-2018\)

             \(\Leftrightarrow y=-1009\)

    So \(y=-1009\).

            

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    We have: \(A=2018^2-2017^2+2016^2-2015^2+...+2^2-1^2\)  

                        \(=\left(2018-2017\right)\left(2018+2017\right)+\left(2016-2015\right)\left(2016+2015\right)+...+\left(2-1\right)\left(2+1\right)\)

                        \(=2018+2017+2016+2015+...+2+1\)

                        \(=\dfrac{2018.2019}{2}=2037171\).

    So the last two digits of A is 71.

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