\[ \beginaligned (x+y)^2 &= x^2 + 2xy + y^2 \\ (x-y)^2 &= x^2 - 2xy + y^2 \endaligned \]
Once you've tested code in TeXer:
Here’s a concise guide covering what it is, how to access it, and basic syntax. texer aops
It looks like you're asking about on the Art of Problem Solving (AoPS) website. \[ \beginaligned (x+y)^2 &= x^2 + 2xy +
You can also manually wrap code with [tex] … [/tex] in posts. how to access it