Anyone please help i have to do expanding expressions and i dont know how to

If f(x)=-x^2+6x-1 and g(x)=3x^2-4x-1,find(f+g)(x)

Clarence wants to buy a new car. he finds an ad for a car that costs 27,200 dollars. suppose his local sales tax is 7%. -how much would he have to pay? -what is the cost of the car including tax? -if clarence has 29,864 saved, can he pay cash to buy the car?

Aright cylinder has a diameter of 8 m and a height of 6m. what is the volume of the cylinder