Multiply the reciprocals of -9/2 and 5/18 and add the additive inverse of -4/5 to the product. What is the result?

Suppose there is a simple index of three stocks, stock abc, stock xyz, and stock qrs. stock abc opens on day 1 with 4000 shares at $3.15 per share. stock xyz opens on day 1 with 5000 shares at $4.30 per share. stock qrs opens on day 1 with 6000 shares at $4.60 per share. the price of stock abc on day 8 begins at $3.50. the price of stock xyz on day 8 begins at $3.90. stock qrs opens on day 8 with a price of $4.50 per share. assume that each stock has the same number of shares that it opened with on day 1. what is the rate of change of this simple index over 1 week?

[15 points, algebra 2]simplify the complex fraction and find the restrictions.

[10 points, algebra 2]according to my answer key the restrictions are -1 and 4. but why not positive 1?