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# Solving quadratic equations — Harder example

Watch Sal work through a harder Solving quadratic equations problem.

## Want to join the conversation?

• Is there an easier way of remembering the quadratic formula, because I have a PSAT coming up and I do not understand half of the stuff on there.
• Or, if songs don't do the trick:

A "negative boy" "couldn't decide" if he should go to "radical" party. Being "square", he decided "not" to go and missed out on (4 awesome chicks). The party was "over" at "2a"m.

Hope this helps too!
• would we be asked to solve these kinds of questions without a calculator ?
• It is best to practice as if you will not have a calculator on these. Besides, it is probably easier to solve many of these without a calculator. As Sal says, we have to do a lot of algebraic manipulation to get the formula to a form that we can solve. Until you have the equation in the right form, the calculator can just get in the way.
• whats the best way to remember the quadratic equation?
• my algebra teacher used to sing to us the quadratic formula to the tune of "pop goes the weasel". ive never forgotten it since. hope that helps (even though im years late)
• I don't understand this. Can someone simplify this for me? If I don't get this, I'm never getting into college. :,(
• At the beginning of the video, why do we need to set the equation equal to zero?Could someone please explain.
• because at first you need to multiply both expression and equal to 5.And then after you could combine like terms; that's the way it works.
• How do you know if you multiply through the parenthesis or if you just use the positive one in front of the parenthesis to distribute? I never ;earned how to do this, I always just inserted the different options into the equation to see what my answer would be....but I don't know how to do that with fractions at all.
I am also not very good with square roots either which is another thing I need help with.
• why isn't it -20 when you plug it in the quadratic equation?
• Not to sound rude, but aside from SATs or becoming a mathematician or teacher, is there any time we would use this kind of math in day-to-day life? I appreciate Khan Academy and everything they do, but I'm a little scared of coming off as rude. Once again, not my intention, just want to know.