3 replies to this topic

[Domuntfal]

Hello. I didn't try or pay attention that hard to math in high school, but now I want to be a programmer. So now I'm in community college and I'm studying PreCalculus trying to test into Calculus so I don't have to take college classes that don't count toward a degree.

I'm currently working on Ellipses and I'm trying to find the foci on this problem.

I'm multiplying a fraction that is √5/3 multiplied by 4. What do you do when you have to multiply a square root where either the numerator or the denominator is a square root by a whole number?

Also, does anyone know any websites that are really good for PreCalculus?

Right now I'm using a book called Advanced Mathematics by Richard G. Brown, but it doesn't go through all the steps. In fact, it doesn't even cover how to find the vertices, or the foci. It usts throws the problems at you.

So I'm kind of piecing stuff together by jumping from website to website trying to find directions.

I was thinking of buying the Pre Calculus book by Blitzen. Is that any good? Thank you very for much for any help in advance.

[Revolt]

Well since 4 = sqrt(16)

4*sqrt(5) = sqrt(16*5) = sqrt(80)

The reasoning behind this is that sqrt(5) = 5^(1/2) and one of the properties regarding powers is that if you multiply two numbers powered to the same number the result is their multiplication powered to that number. That is:
y^x * z^x = (y*z)^x

The same applies to division:
y^x / z^x = (y/z)^x

As for the books I've never had the need to read a Pre Calculus Book so I can't really help you with that.

[WingedPanther]

First of all, the problem you're working on is not PreCalculus, it's Intermediate Algebra. That's why it's skipping a lot of steps.

Second issue: You have to decide on which representation you want the answer in. Ultimately, you're looking at sqrt(5)/3 * 4 = sqrt(5)/3 * 4/1 = sqrt(5)*4 / 3*1.

[Domuntfal]

Thanks so much. I did it your way Panther and it matched the solution in my book. And I didn't know it was intermediate algebra...so I guess I need to go back more. ugh.