Nice illustrations but that article makes the same mistake that a lot of posts of that type often falls to, namely, assuming the reader has a similar background as the author:
> We all know that the slope of a linear equation/function has a constant value
Er... no. We don't "all" know that.
Actually, I'd say that 99.99% of the population of the planet has no idea what that means.
Even the examples provided are kind of Math-heavy (for example, jumping right into the notation of the limit of x^5/25) - enough that a novice would probably feel overwhelmed.
I find that people who are very familiar with a subject usually have a difficult time explaining it without slipping into jargon that will lose the listener.
> We all know that the slope of a linear equation/function has a constant value
Er... no. We don't "all" know that.
Actually, I'd say that 99.99% of the population of the planet has no idea what that means.