give me possibilities on how to make -9

Ok, I'm going to be that one person who gives you a completely impractical possibility for how to make -9.

Here it goes.

(3*7*9*4/6)*(9÷2÷3÷4÷5)-(18.45) = -9

1-10

3(-3)

27/(-3)

-100+91

the square root of 81 (kinda sorta)

[(27)^(2/3)*250/(50*5)+290-14.5*20]*(63/(3^2*-7))

$$(-2-\sqrt{5}i)(2-\sqrt{5}i)=-9$$

Lots of great answers here

On Heureks' vein how about

$$-9=-(13-4)=-(\sqrt{13}-2)(\sqrt{13}+2)=(2-\sqrt{13})(\sqrt{13}+2)$$