Need help with 3 and 4. Also can you check my work?

Checking, it all looks ok except for the range in number 7.
3 is a line with a slope so all reals (which you've written negative infinity to infinity, fine) make up both the domain and range.
4 is a parabola in the usual orientation, so a domain of all reals. There's a minimum so a range of y >= -1.