We are a commune of inquiring, skeptical, politically centrist, capitalist, anglophile, traditionalist New England Yankee humans, humanoids, and animals with many interests beyond and above politics. Each of us has had a high-school education (or GED), but all had ADD so didn't pay attention very well, especially the dogs. Each one of us does "try my best to be just like I am," and none of us enjoys working for others, including for Maggie, from whom we receive neither a nickel nor a dime. Freedom from nags, cranks, government, do-gooders, control-freaks and idiots is all that we ask for.
Algebra, geometry, calculus are all constructs of the white male patriarchy.
2+2=5 is all that is needed and any deviation is coming from an enemy of the state.
Ouroboros Eats Itself
I am old fart. And I would like to learn calculus. I was too flighty in college to apply myself and dropped out of the class after a few weeks. I bombed trigonometry, again, because I was too flighty to apply myself. But went on to have to use it extensively in what was my (eventual) chosen field and have worked around not knowing calculus.
IMHO it depends on two things: The book and the teacher. If you or anyone wishes to learn calculus and don't intend to take a class in it find a good first year text book on it. One with lots of examples and very readable. The Idiot's Guide to Calculus is a good book but not a textbook. If you live near a college you will find used text books in used book stores.
I would suggest that you turn to a page/chapter some 1/4 of the way through the book and read a few pages if it is readable and feels comfortable you may have a winner. You can't always tell from the first couple of chapters. But the authors writing and teaching style is important if you are doing this without a teacher.
In constantly having to solve for unknowns but I'm not sure where quadratic equations get used. If really love to know.
I'm about five years shy of retiring. At those point, I'm mostly interested in learning calculus for the sake of learning calculus. I still have my old college text book. It was actually a pretty good book and it had the answered, so I can check my homework.
Khan Academy will take you from counting to calculus 2 in a long series of reasonably short videos. Geometry, trig, and stats as well. I don't think it's a replacement for a good textbook, but math teachers in K-12 often use his videos to supplement the textbook.
I slightly disagree here. I learned calculus much later in life and it was useful in many ways. But, even if not useful, I found a real enjoyment in the understanding. Calculus describes so much of the physical world.