What is the y-intercept of the line described by the equation y=3x+5

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

Can someone check if i did this correct. it’s number 4 if you’re wondering.

Parabolas y=−2x^2 and y=2x^2 +k intersect at points a and b that are in the third and the fourth quadrants respectively. find k if length of the segment ab is 5.