1.

If the curves `(x^2)/4+y^2=1`and `(x^2)/(a^2)+y^2=1`for a suitable value of `a`cut on four concyclic points, the equation of the circle passingthrough these four points is`x^2+y^2=2`(b) `x^2+y^2=1``x^2+y^2=4`(d) none of theseA. `x^(2)+y^(2)=2`B. `x^(2)+y^(2)=1`C. `x^(2)+y^(2) =4`D. none of these

Answer» Correct Answer - B
Let equation of the circle be `((x^(2))/(4)+y^(2)-1) + lambda ((x^(2))/(a^(2))+y^(2)-1) = 0`
`rArr x^(2) ((1)/(4)+(lambda)/(a^(2))) +y^(2) (1+lambda) =1 +lambda`
`rArr x^(2) ((a^(2)+4 lambda)/(4a^(2))) +y^(2) (1+lambda) =1 +lambda`
`rArr x^(2) ((a^(2)+4 lambda)/(4a^(2)(1+lambda))) +y^(2) = 1`
Clearly, the circle is `x^(2)+y^(2) =1`.


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