What postulate/theorem/ definition do these follow?

Your friend swims on the school team. in his first four races, his times are 24.7, 23.5, 25.6, and 27.2 seconds. which time listed for his next race would make the range larger?

Write numerical coefficient of y² in the expression 2x² - 15xy – 7y²

50 points~ ! i have to turn this in tomarrow