To break even the cost to produce the product, c(x)c(x), must equal the revenue generated by selling the product, r(x)r(x). Therefore,
c(x) = r(x)c(x)=r(x)
or
5x + 18 = 2x^25x+18=2x2
We can now solve this for xx.
5x + 18 - color(red)(5x) - color(blue)(18) = 2x^2 - color(red)(5x) - color(blue)(18)5x+18−5x−18=2x2−5x−18
5x - color(red)(5x) + 18 - color(blue)(18) = 2x^2 - color(red)(5x) - color(blue)(18)5x−5x+18−18=2x2−5x−18
0 + 0 = 2x^2 - 5x - 180+0=2x2−5x−18
0 = 2x^2 - 5x - 180=2x2−5x−18
We can now factor this.
2x^2 - 5x - 18 = 02x2−5x−18=0
(2x - 9)(x + 2) = 0(2x−9)(x+2)=0
We can now solve both of these for 00:
2x - 9 = 02x−9=0
2x - 9 + 9 = 0 + 92x−9+9=0+9
2x - 0 = 92x−0=9
2x = 92x=9
(2x)/2 = 9/22x2=92
x = 9/2x=92
and
x + 2 = 0x+2=0
x + 2 - 2 = 0 - 2x+2−2=0−2
x + 0 = -2x+0=−2
x = -2x=−2
Because you can't produce NEGATIVE units the answer is 9/2 or 4.5 units are needed to be produced to break even.
But because you can't create a 1/2 a unit you need to round up to 5 units.