Step-by-step explanation: divide 750 by 21.5 to figure out how many gallons he would need and than multiply that by $3.15 to find out how much it would cost and you get $109.88
The correct answer is: if is a root of , then is also a root of .
In fact, every polynomial has real and/or complex solutions. If all solutions are real, we're good. But if not all of them are real, then the complex ones come in couple of conjugate solutions. Since and are conjugate complex numbers, if one of them is a solution, the other must be as well.