For the first problem:
You need to find what f(x+h) is before you can solve. Just plug (x+h) into f(x)=1/x^2 just like you would a normal number, so it'll be f(x+h)=1/(x+h)^2. Shouldn't be too hard after that.
Would you mind clarifying the second problem, is that y=2x+5 (what's the -3 doing there?), f(x)=-3, x=0, (-5x?) and x>0?
f(x)=3: "f(x)" is synonymous with "y" so it's just y=-3
finding the domain: find all of the possible x-coordinates (don't be too proud to draw a graph
)
finding the intercepts: set x=0 to find the y-int and y=0 to find the x-int.
Third problem:
It looks too easy so I'm not sure my answer is correct. It's given that h=2r so replace h with 2r leaving you with V(r)= pi*r^2*2r