Don't understand solution to this mock AMC 12?












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I don't get the answer to the solution of the problem.
I understand that k=c+8, but I don't understand why the upper bound of k is when x=0, as x has to be a positive real number. Thanks in advance.










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    0












    $begingroup$


    I don't get the answer to the solution of the problem.
    I understand that k=c+8, but I don't understand why the upper bound of k is when x=0, as x has to be a positive real number. Thanks in advance.










    share|cite|improve this question











    $endgroup$















      0












      0








      0





      $begingroup$


      I don't get the answer to the solution of the problem.
      I understand that k=c+8, but I don't understand why the upper bound of k is when x=0, as x has to be a positive real number. Thanks in advance.










      share|cite|improve this question











      $endgroup$




      I don't get the answer to the solution of the problem.
      I understand that k=c+8, but I don't understand why the upper bound of k is when x=0, as x has to be a positive real number. Thanks in advance.







      algebra-precalculus polynomials






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      edited Feb 3 at 0:56









      J. W. Tanner

      4,7871420




      4,7871420










      asked Feb 2 at 21:09









      varunrvarunr

      1




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          $begingroup$

          If $x<0$ then $x-2<-2,$ so $(x-2)^2>4.$






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          • $begingroup$
            yes, but doesn't x have to be positive?
            $endgroup$
            – varunr
            Feb 3 at 3:39










          • $begingroup$
            If there is a negative root $x,$ then $2(x-2)^2>8$ so if $k<8$ there is no negative root. This doesn't show that there exist two positive roots when $k<8.$ Is that what you're asking?
            $endgroup$
            – saulspatz
            Feb 3 at 4:37










          • $begingroup$
            yes, and it also says that x has to positive in the problem
            $endgroup$
            – varunr
            Feb 5 at 0:17










          • $begingroup$
            @varunr Yes, but as $x$ gets close to to $0$, $k$ gets close to $8$. The length of the open interval $(0,8)$ is $8$.
            $endgroup$
            – saulspatz
            Feb 5 at 3:54












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          active

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          0












          $begingroup$

          If $x<0$ then $x-2<-2,$ so $(x-2)^2>4.$






          share|cite|improve this answer









          $endgroup$













          • $begingroup$
            yes, but doesn't x have to be positive?
            $endgroup$
            – varunr
            Feb 3 at 3:39










          • $begingroup$
            If there is a negative root $x,$ then $2(x-2)^2>8$ so if $k<8$ there is no negative root. This doesn't show that there exist two positive roots when $k<8.$ Is that what you're asking?
            $endgroup$
            – saulspatz
            Feb 3 at 4:37










          • $begingroup$
            yes, and it also says that x has to positive in the problem
            $endgroup$
            – varunr
            Feb 5 at 0:17










          • $begingroup$
            @varunr Yes, but as $x$ gets close to to $0$, $k$ gets close to $8$. The length of the open interval $(0,8)$ is $8$.
            $endgroup$
            – saulspatz
            Feb 5 at 3:54
















          0












          $begingroup$

          If $x<0$ then $x-2<-2,$ so $(x-2)^2>4.$






          share|cite|improve this answer









          $endgroup$













          • $begingroup$
            yes, but doesn't x have to be positive?
            $endgroup$
            – varunr
            Feb 3 at 3:39










          • $begingroup$
            If there is a negative root $x,$ then $2(x-2)^2>8$ so if $k<8$ there is no negative root. This doesn't show that there exist two positive roots when $k<8.$ Is that what you're asking?
            $endgroup$
            – saulspatz
            Feb 3 at 4:37










          • $begingroup$
            yes, and it also says that x has to positive in the problem
            $endgroup$
            – varunr
            Feb 5 at 0:17










          • $begingroup$
            @varunr Yes, but as $x$ gets close to to $0$, $k$ gets close to $8$. The length of the open interval $(0,8)$ is $8$.
            $endgroup$
            – saulspatz
            Feb 5 at 3:54














          0












          0








          0





          $begingroup$

          If $x<0$ then $x-2<-2,$ so $(x-2)^2>4.$






          share|cite|improve this answer









          $endgroup$



          If $x<0$ then $x-2<-2,$ so $(x-2)^2>4.$







          share|cite|improve this answer












          share|cite|improve this answer



          share|cite|improve this answer










          answered Feb 2 at 21:15









          saulspatzsaulspatz

          17.3k31435




          17.3k31435












          • $begingroup$
            yes, but doesn't x have to be positive?
            $endgroup$
            – varunr
            Feb 3 at 3:39










          • $begingroup$
            If there is a negative root $x,$ then $2(x-2)^2>8$ so if $k<8$ there is no negative root. This doesn't show that there exist two positive roots when $k<8.$ Is that what you're asking?
            $endgroup$
            – saulspatz
            Feb 3 at 4:37










          • $begingroup$
            yes, and it also says that x has to positive in the problem
            $endgroup$
            – varunr
            Feb 5 at 0:17










          • $begingroup$
            @varunr Yes, but as $x$ gets close to to $0$, $k$ gets close to $8$. The length of the open interval $(0,8)$ is $8$.
            $endgroup$
            – saulspatz
            Feb 5 at 3:54


















          • $begingroup$
            yes, but doesn't x have to be positive?
            $endgroup$
            – varunr
            Feb 3 at 3:39










          • $begingroup$
            If there is a negative root $x,$ then $2(x-2)^2>8$ so if $k<8$ there is no negative root. This doesn't show that there exist two positive roots when $k<8.$ Is that what you're asking?
            $endgroup$
            – saulspatz
            Feb 3 at 4:37










          • $begingroup$
            yes, and it also says that x has to positive in the problem
            $endgroup$
            – varunr
            Feb 5 at 0:17










          • $begingroup$
            @varunr Yes, but as $x$ gets close to to $0$, $k$ gets close to $8$. The length of the open interval $(0,8)$ is $8$.
            $endgroup$
            – saulspatz
            Feb 5 at 3:54
















          $begingroup$
          yes, but doesn't x have to be positive?
          $endgroup$
          – varunr
          Feb 3 at 3:39




          $begingroup$
          yes, but doesn't x have to be positive?
          $endgroup$
          – varunr
          Feb 3 at 3:39












          $begingroup$
          If there is a negative root $x,$ then $2(x-2)^2>8$ so if $k<8$ there is no negative root. This doesn't show that there exist two positive roots when $k<8.$ Is that what you're asking?
          $endgroup$
          – saulspatz
          Feb 3 at 4:37




          $begingroup$
          If there is a negative root $x,$ then $2(x-2)^2>8$ so if $k<8$ there is no negative root. This doesn't show that there exist two positive roots when $k<8.$ Is that what you're asking?
          $endgroup$
          – saulspatz
          Feb 3 at 4:37












          $begingroup$
          yes, and it also says that x has to positive in the problem
          $endgroup$
          – varunr
          Feb 5 at 0:17




          $begingroup$
          yes, and it also says that x has to positive in the problem
          $endgroup$
          – varunr
          Feb 5 at 0:17












          $begingroup$
          @varunr Yes, but as $x$ gets close to to $0$, $k$ gets close to $8$. The length of the open interval $(0,8)$ is $8$.
          $endgroup$
          – saulspatz
          Feb 5 at 3:54




          $begingroup$
          @varunr Yes, but as $x$ gets close to to $0$, $k$ gets close to $8$. The length of the open interval $(0,8)$ is $8$.
          $endgroup$
          – saulspatz
          Feb 5 at 3:54


















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