Which of the following statements regarding the expansion of (x+y)^n are correct a. the coefficients of x^n-1 and y^n-1 both equal one
b. the coefficients of x^n and y^n both equal 1
c. for any term x^ay^b in the expansion, a+b=n
d. for any term x^ay^b in the expansion, a-b=n

When rates are expressed as a quantity of 1, such as 2 feet per second or 5 miles per hour, they are called unit rates. if you have a multiple-unit rate such as 120 students for every 3 buses, and want to find the single-unit rate, write a ratio equal to the multiple-unit rate with 1 as the second term.