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8th Class Mathematics Algebraic Expressions Question Bank Algebraic Expressions and Identities

  • question_answer
    If (x - 5) notebooks cost Rs. \[({{x}^{2}}-13x+40)\], what is the cost of one notebook?

    A)  \[(x-1)\]                      

    B)  \[(x-2)\]          

    C)  \[(x-6)\]          

    D)         \[(x-8)\]          

    Correct Answer: D

    Solution :

    Cost of \[(x-5)\] notebooks is \[({{x}^{2}}-13x+40)\]To calculate the cost of 1 notebook, we factorize \[({{x}^{2}}-13x+40)\] \[{{x}^{2}}-13x+40={{x}^{2}}-8x-5x+40\] \[=x(x-8)-5(x-8)=(x-8)(x-5)\] \[\therefore \]Cost of one notebook\[=(x-8)\times \frac{(x-5)}{x-5}\] \[=x-8\]


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