12th Class Mathematics Applications of Derivatives Question Bank Case Based (MCQs) - Derivatives

  • question_answer
    L.H.D. of \[f\left( x \right)\] at \[x=1\] is

    A) 1

    B) -1

    C) 0

    D) 2

    Correct Answer: B

    Solution :

    We have, \[Rf'\left( 1 \right)=\underset{h\to 0}{\mathop{\lim }}\,\frac{f\left( 1-h \right)-f\left( 1 \right)}{-h}\] \[=\underset{h\to 0}{\mathop{\lim }}\,\frac{-1}{h}\left[ \frac{{{\left( 1-h \right)}^{2}}}{4}-\frac{3\left( 1-h \right)}{2}+\frac{13}{4}-2 \right]\] \[=\underset{h\to 0}{\mathop{\lim }}\,\left( \frac{1+{{h}^{2}}-2h-6+6h+13-8}{-4h} \right)\] \[=\underset{h\to 0}{\mathop{\lim }}\,\left( \frac{{{h}^{2}}+4h}{-4h} \right)=-1\]


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