Question:
Rewrite the function to reveal when sales of compact discs and $0.
Answer:
The cost in 2010 is $0
Step-by-step explanation:
Given
[tex]C(x) = -2x^2 + 38x + 40[/tex]
Required
Find x when [tex]C(x) = 0[/tex]
This gives:
[tex]C(x) = -2x^2 + 38x + 40[/tex]
[tex]-2x^2 + 38x + 40=0[/tex]
Expand
[tex]-2x^2 + 40x -2x+ 40=0[/tex]
Factorize:
[tex]-2x(x - 20) -2(x- 20)=0[/tex]
[tex](-2x - 2)(x- 20)=0[/tex]
Solve for x
[tex]-2x-2=0\ or\ x - 20 = 0[/tex]
[tex]x = -1\ or\ x = 20[/tex]
x represents time. So, it cannot be negative.
[tex]x = 20[/tex]
20 years after 1990 is: 2010. Hence, the cost in 2010 is $0
