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The function C(x) = -2x2 + 38x + 40 models the sales, in hundreds of

millions of dollars, of compact discs for years since 1990.

Sagot :

MrRoyalidn

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

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