The function C(x) = -2x2 + 38x + 40 models the sales, in hundreds of millions of dollars, of compact discs for years since 1990.

Question:

Rewrite the function to reveal when sales of compact discs and $0.

The cost in 2010 is $0

Step-by-step explanation:

Given

Required

Find x when

This gives:

Expand

Factorize:

Solve for x

x represents time.  So, it cannot be negative.

20 years after 1990 is: 2010. Hence, the cost in 2010 is $0

x ≥ 18 is your answer

step-by-step explanation:

let "a number" = x

(2/3)x + 17 ≥ 29

isolate the variable (x). do the opposite of pemdas (parenthesis, exponent (& root), multiplication, division, addition, subtraction).

first, subtract 17 from both sides.

(2/3)x + 17 (-17) ≥ 29 (-17)

(2/3)x ≥ 29 - 17

(2/3)x ≥ 12

next, multiply 3/2 to both sides to isolate the x

(3/2)(2/3)x ≥ 12(3/2)

x ≥ 12(3/2)

simplify. multiply, then divide

x ≥ (12 * 3)/2

x ≥ (36)/2

x ≥ 18

x ≥ 18 is your answer

~