10th Class Mathematics Related to Competitive Exam Question Bank Algebra

  • question_answer
    If \[x\] satisfies \[|x-1|+|x-2|+|x-3|\,\,\,\ge 6\], then

    A)  \[0\le 0\le 4\]                  

    B)         \[x\le 0\,\,or\,\,x\ge 4\]  

    C)  \[x\le -2\,\,or\,\,x\ge 4\] 

    D)         \[x\ge -2\,\,or\,\,x\le 4\]

    Correct Answer: B

    Solution :

                    \[|x-\alpha |=x-\alpha \]if\[x\ge \alpha \]                            \[=\alpha -x\]if\[x\le \alpha \] Now mark \[1,\,\,2\] and \[3\] as shown and the regions as I.             \[x\le 1\] II.            \[1\le x\le 2\] III.           \[2\le x\le 3\] IV.          \[x\ge 3\] and discuss the inequation in all these regions. Region I. Since\[x<1\], therefore given inequation is \[(1-x)+(2-x)+(3-x)\le 6\] or            \[-3x\ge 0\] or            \[x\le 0\] \[\therefore \]  \[x\le 1\] and        \[x\le 0\] or            \[x\le 0\] Region II. Since \[1\le x\le 2\] therefore given inequation is                 \[(x-1)+(2-x)+(3-x)\ge 6\] or            \[4-x\ge 6\] or            \[x\le -2\] It is impossible to find\[x\]such that \[1\le x\le 2\]    and        \[x\le -2\]. Region III. Since\[2\le x\le 3\], therefore given inequation is                 \[(x-1)+(x-2)+(3-x)\ge 6\] or            \[x\ge 6\] Here also it is impossible to find \[x\] such that \[2\le x\le 3\] and\[x\ge 6\] Region IV. Since\[x\ge 3\], therefore given inequation is                 \[(x-1)+(x-2)+(x-3)\ge 6\] or            \[x\ge 4\] \[\therefore \]  \[x\ge 3\] and        \[x\ge 4\] or            \[x\ge 4\] \[\therefore \]  \[x\]will satisfy\[x<0\] or            \[x\ge 4\]


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