Which relation is correct for an isochoric process?

The angle between the lines whose direction cosines satisfy the equations $l + m + n = 0$ and $l^2 = m^2 + n^2$ is

If the difference between the roots of the equations $x^2+ax+b=0$ and $x^2+bx+a=0$ is the same,and $a \neq b$,then:

What is the maximum number of rectangular components into which a vector can be split in space?

The intercepts on the $x$-axis made by the tangents to the curve $y = \int_0^x |t| dt, x \in R$ which are parallel to the line $y = 2x$ are equal to:

The number of proper subsets of the set ${1, 2, 3}$ is