What is the length of the focal width x=-1/8y^2

The standard equation is 4p(x-h) = (y-k)^2 where |p| = focal distance |4p| = focal width.

x=-1/8y^2
-8x=y^2
4*(-2)(x-0) =( y-0)^2

p = -2, h=0, k=0

focal width = |4*(-2)| = 8

The answer to your question is that the length of the focal width is equal to 8.

Rounding decimals is very similar to rounding other numbers. if the hundredths and thousandths places of a decimal is forty-nine or less, they are dropped and the tenths place does not change. for example, rounding 0.843 to the nearest tenth would give 0.8. , your welcome !

With a continuous thought process.