Answer:
see below
Explanation:
The Desmos graphing utility is available as an app for phone or tablet from the app stores for Android and Apple devices. It is available from the desmos web site by clicking on "Graphing Calculator" on the home page.
Attached is a screen-shot of the web version. Help can be found under the (?) button at upper right. I found the help to be useful when first starting or when trying to do something I haven't done before.
You can create an account, if you like, but that is not necessary to obtain all of the basic functionality.
A link for sharing a graph will be generated by clicking on the icon to its left. Graphs can also be saved for later reference, if you have an account. The link to a graph will work whether you have an account or not.
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There are other desmos tools available, too, for general calculation, geometrical construction, and matrix manipulation. (I have not yet used those.)
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Desmos likes to use x and y for the independent and dependent variables, respectively. You can define something like h(t) = 5t+1 and it will graph it as though it were y=5x+1. When you click on an equation or graph, points of intersection with other graphs or with the axes will be highlighted. Clicking on those highlights will give their coordinates.
Equations don't need to be of the "y=" form. For example, you can use x^2+y^2=1 to make a unit circle. The usual math symbols work for keyboard input (* for multiplication; / for division; ^ for exponents). The tab or arrow keys move out of denominator or exponent fields. To make more complicated exponents, parentheses help.
There's so much more it can do. It is worthwhile to visit the on-line tutorial information.