Question

Can someone please explain the algebraic steps in between? (Physics, The Law of Biot-Savart)

Answer 1

I get that
$$\frac{y}{y^{2}}$$
Is the same thing as
$$ y^{-1} $$
or
$$ \frac{1}{y} $$

Answer 2

So I guess my two questions as - where does the x go, and how does $$4\pi$$ turn into $$2\pi$$ ?

Answer 3

two questions are*