MCQ
A variable circle passes through the fixed point $(2,0)$ and touches the $y$-axis . Then the locus of its centre is
- AA circle
- BAn Ellipse
- CA hyperbola
- ✓A parabola
$\therefore $ radius of circle = $h$
Now ${(h - 2)^2} + {k^2} = {h^2}$
$ \Rightarrow $${h^2} + 4 - 4h + {k^2} = {h^2}$
$ \Rightarrow $ ${k^2} = 4h - 4$.
Hence the locus of centre is ${y^2} = 4x - 4$, which is a parabola.
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If $8 x^{2}+b x+c=0$ is a quadratic equation whose roots are $\alpha^{1 / 5}$ and $\beta^{1 / 5}$, then the value of $c-b$ is equal to: