Question

The expression -x^2 + 70x -600 represents a companys profit for selling x items. For which number of items sold is the companys profit equal to zero?

Answer 1

Explanation:

-x² + 70x - 600

If we multiply all by -1, we have

x² - 70x + 600

If we factorise this, we have

x² - 10x - 60x + 600

x(x - 10) - 60(x - 10)

(x - 10) (x - 60)

x = 10

x = 60

If the company sells 10, or 60 items, their profit is 0