What's the sum of 6+y

Brook states that the distance on the line is 4 units. caleb states that the whole line does not have a distance because it continues on forever. vivian states that the line is 6 units long. which distance did brook measure? which distance did vivian measure?

When you answer this can you explain

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