3.
There can (and have to) be two values which bring in a monthly revenue of $1200. This is because of the very nature of quadratics in that every one has 2 answers (unless it has complex roots). So, if you actually factor the quadratic, and plug in $1200 for the y-value, you'll get 2 x-values.
5.
Since it's a right triangle, you can set it up as follows:
[tex]x^2+(x+10)^2 = 75^2[/tex]
Now, we'll just solve for x, which is the distance of Train 1. To do that, just simplify the equation first:
[tex]x^2 = 75^2-(x+10)^2[/tex]
I can square root both sides to get:
[tex] x = \sqrt{-(x+85)+(x-65)} [/tex]
So, that's how far the first train traveled, and the second train just traveled:
[tex] x = \sqrt{-(x+85)+(x-65)}+10 [/tex]
