Can someone give me factors of 9900 that add up to 400?

Question

its a quadratic equation. can i learn a sort cut? thanks

-x^2+400x=900

Answer 1

Try this:
-x^2 + 400x = 9,900
x^2 - 400x + 9,900 = 0
x^2 - 400x + 200^2 - 200^2 + 9,900 = 0
(x^2 - 200)^2 - 40,000 + 9,900 = 0
(x^2 - 200)^2 - 30,100 = 0
(x^2 - 200 - 10√301)(x^2 - 200 + 10√301) = 0
Using your later equation,
-x^2 + 400x = 900
(x^2 - 200)^2 - 39,100 = 0
(x^2 - 200 - 10√391)(x^2 - 200 + 10√391) = 0

Answer 2

um....400 and 0? no, wait, that's how much I pay to fill my gas tank and how much money I have in the bank AFTER I fill my tank. My bad......