Math Is Fun Forum

2 log (x+2) + log (x - 1) = 3 log x            using a base of 3.

I'm supposed to solve for X. Usually I'm pretty good with these but this I just can't solve. Usually I have to factor, but I keep ending up with a 3rd degree polynomial which my mathbook has not taught me how to solve. So I'm expected to solve it another way. Help! :-(

Playing basketball at the park yesterday, and there was a kid on a bench doing his homework. "I hope he's doing math" I thought, "and I hope he needs help!"

suddenly he asked his friends "how many feet are in a mile?" his friends didn't know. Thats philadelphia for ya. lol. So I spoke up, "5280". Next thing I knew I was helping the kid with his homework. He was only in like 8th grade, I'd much have prefered he'd been in highschool and doing highschool level math, (more fun!) but it was still nice to be able to help.

I could probably make a fortune teaching n00bs math in philadelphia!

I'm teaching my younger brother 6th grade math and my younger sister Algebra 2 this year. w00t! Teaching math is fun!

I'm pretty sure its called omega, it looks like a w drawn with curves. Or kind of like a horizontal "8"

I've seen this symbol several times. What does it mean? My mathbook used it once to stand for radians per second, in angular velocity problems. But I tend to see it a lot in places where its meaning appears to be undefined.

What does this symbol stand for? Is it just used for variables or does it always mean the same thing?

Ok you gotta admit this show is cool but I don't always know if this guy is talking math or if someone is just making this math up but, well he gave a wierd probability example that doesn't make sense..

You are at a gameshow and there are three curtains before you. Behind one curtain is a goat, behind the other curtain is a car, and behind the other is another goat.

The object is to guess the curtain which has the car behind it, and you win it.

Now obviously the chances on the first guess, are 1/3. (One choice three possibilities.)

Now a contestent pics the center curtain. A side curtain is opened, revealing a goat. So one curtain is eliminated and you know that the car is either behind the curtain you picked, or the other curtain. NOW will switching your choice improve your chances of winning the car? It would appear, that either way, your chances are the same. 50-50. But according to Mr Charlie Eps, you'd be wrong. Unfortunatly he explained why so quickly I couldn't follow it. But he said that switching your choice at that point, actually doubles your chances of winning the car. Something about revealing a goat in the other curtain increases the odds of a goat being in the location you picked. Why, I have no idea, I couldn't follow it that quickly.

Has anyone ever heard of this problem? Can you justify why switching your choice after the goat is revealed in the other curtain, doubles your chances?

I got a wierd problem today I wasn't sure how to solve. It seems to be a wierd combination of probability and permutations. (or combinations)

Three cards are drawn at random from a deck of 52 cards. (without replacement) What is the probability that two cards will be black and one will be red?

Now obviously there are 26 blacks and 26 reds. The chance of getting a black on the first try is 26/52 or 1/2, on the second draw, since one black card is missing the chances are 25/51, on the third draw there are 50 cards in the deck, but still 26 reds, so 26/50

So 26/52 * 25/51 * 26/50 The answer reduces to 13/102.

But obviously this is not correct. Since it merely said the probability of getting two blacks and one red, regardless of what order they appear in.

Now in permuations, I learned to eliminate repeated combinatons (regardless of order) by dividing by the number of objects in each combination. In This case 3. But I didn't learn how to do it in probability questions. :-/

If I multiply 13/102 by 1/3 (dividing by 3) then we have 13/306. This is obviously not the answer since the demoninator just got larger. The odds should get greater if order does not matter, not less. I checked the anawer to the problem and it says 13/34. Now the only way to get this is to divide the denominator by 3. However I realized I can achieve the same result by dividing the whole expression by 3:  (13/102)/3. This will multiply the numerator by 3 and it can be reduced to 13/34.

Is this the correct way to solve the problem?

On the dark discussion forum, are we allowed to talk about anything? Or just futeristic stuff and head transplants?