## Algebra: A Combined Approach (4th Edition)

The demand equation is as follows: $p=-x^2+15$ where, p = unit price and x = demand The price is given as 7 dollars per pair. Therefore, the equations becomes- $7=-x^2+15$ Step 1: Subtract 15 from both sides of the equation $7-15=-x^2$ $-8=-x^2$ Step 2: Divide both sides by $-1$ $8=x^2$ Step 3: use the square root property: $±\sqrt 8=x$ $x= ±\sqrt{4\times2}$ $x= ±2\sqrt{2}$ $x= ±(2\times1.4142)$ $x=±2.8284$ Since the demand cannot be negative, there is a demand for approximately 3 desk lamps.