"Write the following expressions in the form $X^2 − A^2$ using the method of completing the square."
"1) $x^2 + 8x + 9$"
I don't understand how that can be, but I did try to do it, with no obvious next steps.
$x^2 + 8x + 16 -16 + 9$
$(x + 4)^2 - 7$
I completed the square, but how can I put that in the form $X^2 - A^2$?