JEE Main & Advanced Mathematics Definite Integration Question Bank Self Evaluation Test - Application of Integrals

  • question_answer
    What is the area bounded by the curve \[y=4x-{{x}^{2}}-3\] and the x-axis?

    A) 2/3 sq. unit

    B) 4/3 sq. unit

    C) 5/3 sq. unit

    D) 4/5 sq. unit

    Correct Answer: B

    Solution :

    [b] Given curve is \[y=4x-{{x}^{2}}-3\] Since, area bounded by x-axis \[\therefore y=0\] \[\Rightarrow 4x-{{x}^{2}}-3=0\Rightarrow {{x}^{2}}-4x+3=0\] \[\Rightarrow {{x}^{2}}-3x-x+3=0\Rightarrow (x-3)(x-1)=0\] \[\Rightarrow x=1,3\] \[\therefore \] Required area \[=\int_{1}^{3}{(4x-{{x}^{2}}-3)dx}\] \[\left. =\frac{4{{x}^{2}}}{2}-\frac{{{x}^{3}}}{3}-3x \right|_{1}^{3}=\left( \frac{36}{2}-\frac{27}{3}-9 \right)\] \[-\left( \frac{4}{2}-\frac{1}{3}-3 \right)\] \[=(18-9-9)-\left( 2-\frac{10}{3} \right)=0-\left( \frac{-4}{3} \right)=\frac{4}{3}\] sq. unit.


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