#deckourhellwithboughsofcrowley

Ah, don't worry! It's a quadratic equation so a look at the binomial theorems should help:

We've got three parts and no minus so we'll use the first one.

Let's compare out terms with the ones from the theorem:

a² → x²

b² → 16y²

2ab → 8xy

Now we can easily figure out that

a = x

b = 4y

So our (a+b)² = (x+4y)² 

To check whether that’s really right, we also check whether the middle part is correct:

2ab = 2*x*4y = 8xy

It's correct :D