What is the product of (2x+9) (x+1)? and you.

2x^2 + 11x + 9 

You can foil it to get the correct answer, (FOIL = First, Outter, Inner, Last)

First, lets assume x = 5, to start us off.
(2 * 5 + 9) = (5 + 1)
(I assume that in between the two equations is an = sign because without it, the entire problem would make no sense.)
(10 + 9) = (6)
19 = 6
Not the same. So, I think that it would be lower than 5. Let us continue

x = 3?
(2 * 3 + 9) = (3 + 1)
(6 + 9) = 4
15 = 4

Even lower, maybe a negative.

x = -5?
(2 * -5 + 9) = ( -5 + 1)
(-10 + 9) = -4
-1 = -4

Almost there,

x = -10?

(2 * -10 + 9)  = ( -10 + 4)
( -20 + 9 ) = -8
-11 = -8

It is higher that -10.

x = -7?

(2 * -7 + 9) = ( -7 + 1)
(-14 + 9) = -6
-5 = -6

So very close,
x = 7.5?
( 2 * -7.5 + 9 ) = ( -7.5 + 1)
(-15 + 9 ) = -6.5
-6 = 6.5
EXTREMELY CLOSE,
x = 7.75?
( 2 * 7.75 + 9 ) = ( -7.75 + 1 )
(-15.5 + 9 ) = -6.75
-6.5 = -6.75
i.. nvm..
x = -7.8?
(2 * -7.8 + 9) = ( -7.8 + 1)
(-15.6 + 9) = -6.8
-6.6 = -6.8
om

by this point i realized i was doing it wrong again.. q.q
here is the correct way to do it:
(2x+9) = (x+1)
(2x+9) -- (-- x -- 9) - (x+1) -- (-- x -- 9)
2x + 9 - x - 9 = x + 1 - x - 9
2x - 9 + x + 9 = x - 1 + x + 9
2x - x + 9 - 9 = x - x + 1 - 9
x= -8

The answer is that the rate of change is $50 per 1 monthhope this ; )