If the price elasticity of demand is -1

Since the sign of the elasticity is negative we know that the quantity demanded will decrease as prices increase. Given the information in the text, price elasticity is greater than one in absolute value. Hence, we have elastic demand, i.e. the quantity demanded will react more strongly to changes in the price. To be more precise, if prices will increase by 1%, the quantity demanded will decrease by 1.25%.

Let us assume a company that will increase its prices by 10% in an attempt to increase revenues. As revenues are defined as quantity demanded times prices, a 10% increase in prices leads to a 12.5% reduction in the quantity demanded. Overall, revenues will hence decrease, or, put differently, the negative quantity effect will dominate the positive price effect.