Please use markdown formatting:

(x - 2y) * (x + 2y) = x * x + x * 2y - 2y * x - 2y * 2y = x * x + (x * 2y - 2y * x) - 2y * 2y = x * x - 4y * y

or KaTeX:

$ (x - 2y) * (x + 2y) = x * x + x * 2y - 2y * x - 2y * 2y = x^2 + (x * 2y - 2y * x) - 4y^2 = x^2 - 4y^2 $

to write mathematical formulas.

(x - 2y) * (x + 2y) = xx + x2y - 2yx - 2y2y = xx + (x2y - 2yx) - 2y2y = xx - 4yy

because a^2 - b^2 = (a+b)(a-b).
This is an algebraic identity - the difference of two squares
In your case, you can treat x =a, and b = 2y.

https://mste.illinois.edu/dildine/times/diff2sq.pdf

hhhhh

It would be redundant: https://en.wikipedia.org/wiki/Product_(mathematics)

Please use a spoiler flag.

Your code has a bug, it's missing a { Compare the initial code to yours:

function litres(time) {
  return 0;
}

Your code has a syntax error. Not a kata issue. Next time, please use a spoiler flag when you post code so that users who didn't solve the kata cannot see i (I added the flag for you this time).

.

Don't use ISSUE tag for these kind of questions, mods will tell you that issue is for issues with the kata not for small problems with your code/solution.

There is nothing wrong with the kata - you need to understand error message: the code that appears after "Expected: bla bla" is what you are returning, and the code after "to Deeply Equal: xyz" is the expected correct answer.

As you can see in the example you have pasted above, your answer is not correct - it's that simple really.