Railways Sample Paper RRBs Assistant Loco Pilot and Technician CBT STAGE-I Sample Paper-13

  • question_answer
    The factor form \[({{a}^{4}}{{b}^{4}}-16a{{c}^{4}})\] is

    A)  \[4({{a}^{2}}{{b}^{2}}-4{{c}^{2}})(ab-2c)(ab+2c)\]

    B)  \[({{a}^{2}}{{b}^{2}}-4{{c}^{2}})(ab+2{{c}^{2}})\]

    C)  \[({{a}^{2}}{{b}^{2}}+4{{c}^{2}})(ab+2c)(ab-2c)\]

    D)  \[({{a}^{2}}{{b}^{2}}-4{{c}^{2}})(ab+2c)(ab-4c)\]

    Correct Answer: C

    Solution :

    \[({{a}^{4}}{{b}^{4}}-16{{c}^{4}})=[{{({{a}^{2}}{{b}^{2}})}^{2}}-{{(4{{c}^{2}})}^{2}}]\] \[=({{a}^{2}}{{b}^{2}}+4{{c}^{2}})[({{a}^{2}}{{b}^{2}}-4{{c}^{2}}]\] \[=({{a}^{2}}{{b}^{2}}+4{{c}^{2}})[{{(ab)}^{2}}-{{(2c)}^{2}}]\] \[=({{a}^{2}}{{b}^{2}}+4{{c}^{2}})[{{(ab)}^{2}}-{{(2c)}^{2}}]\] \[=({{a}^{2}}{{b}^{2}}+4{{c}^{2}})(ab+2c)(ab-2c)\]


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