Which of the following halogen oxides is ionic?

The equation of the parabola with focus $(0, 0)$ and directrix $x + y = 4$ is

$A$ man is standing on a balance and his weight is measured. If he takes a step in the left side,then his weight

$A$ ball is let fall from a height $h_0$. It makes $n$ collisions with the earth. After $n$ collisions it rebounds with a velocity $v_n$ and the ball rises to a height $h_n$. Then the coefficient of restitution is given by:

Which of the following is used in optical fibres?

The point where the line $\frac{x - 1}{2} = \frac{y - 2}{-3} = \frac{z + 3}{4}$ meets the plane $2x + 4y - z = 1$ is: