Let's start making our expression.
Just take the number 40 and change it around.
[tex]40=49-9[/tex]
That's a good start.
49 is equal to 7×7, or 7². 9 is equal to 3×3, or 3².
So we can also write this as
[tex]7^2-3^2[/tex]
You can really do whatever you want with it as long as it's still 40, just make sure you've got an exponent there. Here's another example.
[tex](10-3)^2-\sqrt{81}[/tex]
