I just want to check to make sure I am correct --

Question

my equation is y = -x^2 + 90x - 800
If x = 100, -x^2 would be 10,000, not -10,000? Because -100 x -100 is 10,000, not -10,000 --- my calculator keeps giving me a negative number.

So my overall number is 18,200

Answer 1

NO
-x^2 is the same as
-1 * x^2
=-1 * 10,000
= -10,000

Answer 2

In other words your calculator won the argument this time :)