Answer:
The domain of the given parabola in all real numbers.
Step-by-step explanation:
You need to understand what the domain of a function is. The idea is really simple when you know what a function is.
Function is, one could say, a machine, which for a given input produces an output. Real world expamle: a kettle is a kind of a function: you pour cold water into the kettle to have hot water. The kettle changes cold water into hot water. Function is something that changes one thing into something else. In math we play with numbers.
Parabola is a function. Lets see how it works in this example.
I want to know what, lets say number 1 is changed by given parabola into.
I'm beginning from number 1 which is written on X (horizontal) line.
I'm looking for a part of blue line which is exactly below or above.
Exactly above is the point which is marked on the drawing as the blue dot. When I go to the left from that point I reach number 2 on the Y line. I have my answer: given parabola changes 1 into 2.
Long story short: the domain is every number you can put into the kettle.
We know that we can calculate output for any real number for a given parabola, although only small part of it (the blue line) fit the diagram.
