I saw this shirt advertised as a designated Christmas gift for math teachers.

I’m sorry, but this is bad math. If I were a math teacher and received this shirt, I would be horrified.
I understand that the designer meant to reference the song “We Wish You a Merry Christmas,” specifically the line, “Fa lalalalalalalala.”
HOWEVER, that equation would require simple multiplication, NOT the use of an exponent. La to the eighth power would be FAR too many la’s.
It should be Fa + (8La).
As you can see, I spent WAY too much time thinking about this.
UPDATE: 10 NOVEMBER
My 13-year-old son got in the car today after school and said his math class was radical today.
“Get it?” he added. “RADICAL?”

Ah, I see the nerd apple does not fall far from the nerd tree…