Question

A clothing store determines that in order to sell x shirts, the price per shirt should be p(x)=100−x dollars. Getting x shirts from the supplier costs the store C(x)=1,600+20x dollars. If the store’s revenue from selling x shirts is R(x)=x⋅p(x), for what value of x will the store’s cost and revenue be equal?

Answer 1

x= -40

Explanation:

Cost

C(x)=1,600+20x

P(x)=100-x

Revenue=x*p(x)

=x*(100-x)

=100x-x^2

Cost=Revenue

1600+20x=100x-x^2

1600+20x-100x+x^2=0

1600-80x+x^2=0

Solve using quadratic formula

Formula where

a = 1, b = 80, and c = 1600

x=−b±√b2−4ac/2a

x=−80±√80^2−4(1)(1600) / 2(1)

x=−80±√6400−6400 / 2

x=−80±√0 / 2

The discriminant b^2−4ac=0

so, there is one real root.

x= −80/2

x= -40