Something like (n4)
N representing the number before. For example, if n=9 then (9*4)=36.
Hope it makes since for you. I know there might be more to it, but that's what I know off the top of my head.
You can make the equilateral triangle into a right triangle by cutting it in half. So, your sides would be 4.5, 9, and x.
Using Pythagorean Theorem, you know that a^2 + b^2 = c^2.
The 'a' would be equal to 9, and 9^2 is equal to 81.
B is equal to 4.5, and 4.5^2 is 20.25.
So, you have the following:
81 + 20.25 = c^2
And that makes 'c' equal to 101.25.
The square root of 101.25 is approximately equal to 10.06.
So now you know the height, 10.06.
Simplified it is 4k = -14
