Is x+6 a factor of f(c)=-x^2+6x?

What is the number 321,000,000 in scientific notation? also what is the number? ?

1mile equals approximately 1.6 kilometers. which best approximates the number of miles in 6 kilometers?

Jada has a meal in a restaurant she adds up the prices listed on the menu for everything they ordered and gets a subtotal of $42.00. when the check comes, it says they also need to pay $3.99 in sales tax. what percentage of the subtotal is the sales tax