JEE Main & Advanced JEE Main Paper (Held On 25 April 2013)

  • question_answer
                    The equation of a plane though the of intersection of the planes \[x+2y=3,\]of the planes \[x+2y=3,\]\[y-2z+1=0\] and perpendicular to the first plane is:     JEE Main Online Paper ( Held On 25  April 2013 )

    A)                 \[2x-y-10z=9\]  

    B)                                        \[2x-y+7z=11\]

    C)                                        \[2x-y+10z=11\]

    D)                                        \[2x-y-9z=10\]

    Correct Answer: C

    Solution :

                    Equation of a plane through the line of intersection of the planes \[x+2y=3,y-2z+1=0\]is \[(x+2y-3)+\lambda (y-2z+1)=0\] \[\Rightarrow \]\[x+(2+\lambda )y-2\lambda (z)-3+\lambda =0\]             (i) Now, plane (i) is \[\bot \] to x + 2y = 3 \[\therefore \]Their dot product is zero i,e. \[1+2(2+\lambda )=0\Rightarrow \lambda =-\frac{5}{2}\] Thus, required plane is \[x+\left( 2-\frac{5}{2} \right)y-2\times \frac{-5}{2}(z)-3-\frac{5}{2}=0\] \[\Rightarrow \]\[x-\frac{y}{2}+5z-\frac{11}{2}=0\]\[\Rightarrow \]\[2x-y+10z-11=0\]


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