Rearrange y=(X+3)^2 to make x the subject?

What you really need is the prerequisite for this class. "Rearrange" and "Subject" apply to English. In math we say "Solve for x." Never confuse math with English.

First add spaces to improve readability.

y = (X + 3)^2

Take the root.

√y = x + 3

Subtract 3.

√y - 3 = x

Now you have something called a snake. That means you are going to get bit if you don't notice it. The root of y can be either + or -.

x = ±√y - 3

A function is defined as any process that yields one output value for each input value. In this case y is a function of x, but x is not a function of y.