JEE Main & Advanced JEE Main Paper (Held On 12-Jan-2019 Evening)

  • question_answer
    The tangent to the curve \[y={{x}^{2}}-\text{5}x+5,\]parallel to the line \[2y=4x+1,\]also passes through the point [JEE Main Online Paper Held On 12-Jan-2019 Evening]

    A) \[\left( \frac{7}{2},\frac{1}{4} \right)\]

    B)                           \[\left( \frac{1}{4},\frac{7}{2} \right)\]

    C) \[\left( -\frac{1}{8},7 \right)\]                  

    D)   \[\left( \frac{1}{8},-7 \right)\]

    Correct Answer: D

    Solution :

    Here, curve is \[y={{x}^{2}}-5x+5\]\[\Rightarrow \]\[\frac{dy}{dx}=2x-5\] Since, the tangent is parallel to the line \[2y=4x+1\] \[\therefore \]\[\frac{dy}{dx}=2x-5=2\]\[\Rightarrow \]\[x=\frac{7}{2}\] When \[x=\frac{7}{2},y={{\left( \frac{7}{2} \right)}^{2}}-5\times \frac{7}{2}+5=\frac{-1}{4}\] \[\therefore \]Equation of tangent at \[\left( \frac{7}{2},\frac{-1}{4} \right)\]is \[\left( y+\frac{1}{4} \right)=2\left( x-\frac{7}{2} \right)\]\[\Rightarrow \]\[y-2x+\frac{29}{4}=0\] Only the point in option i.e., \[\left( \frac{1}{8},-7 \right)\]satisfies the above equation.


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