Math problem help-please

[Spider-Bite]

Which of the following in a factored form of
2 2
-8x y + 12xy ?



The answer is 4xy(-2x + 3y)

The analysis is

If you examine the two terms, you'll see that 8 and 12 have a common
2 2
factor of 4, and x y and xy have a common factor of xy. So factor out 4xy: 4xy(-2x + 3y)




This is from a ACT prep test book. There's a lot of math I don't know how to do, because I basically bummed my way through school, smoking weed in the bathroom, and really hated math. I absolutely do not understand how they got the answer they got, or how I'm supposed to know how to do what to get to that answer.

Can anybody help me understand this?

 

[Spider-Bite]

I'm steeping out to have a cigarette while I wait a few minutes for people to check this out. So I'll be gone for about five minutes. All help is appreciated, I know it's probably boring, and you have nothing to gain by helping me.

 

[jaguarr]

Do your own homework.

jag

 

[Catman]

I hate math! I hate math so much that one of my first threads back in 2002 was called, "Algebra sucks!"

 

[Lackey]

we'll start here...

do you understand the term "common factor"

do you understand that 4 is a common factor of 8 and 12?

 

[Spider-Bite]

we'll start here...

do you understand the term "common factor"

do you understand that 4 is a common factor of 8 and 12?

first off thanks for taking your time here.

I think so, but I just realized that the math problem didn't show up here the way it was supposed to, so I'm scanning it real quick to post it. give me a second.

 

[Catman]

we'll start here...

do you understand the term "common factor"

do you understand that 4 is a common factor of 8 and 12?

Lackey is a math whiz

 

[JStorm]

-8xy + 12xy
4xy(-2 + 3)

The common factor is 4xy because 4xy goes into -8xy 2 times, and 12xy 3 times.
Hence a 4xy on the outside of the parentheses, and (-2 + 3) on the inside of the parentheses.

I just edited and this problem looks weird. I believe you said you would scan the material, so I will wait.

 

[Spider-Bite]

we'll start here...

do you understand the term "common factor"

do you understand that 4 is a common factor of 8 and 12?

okay here is the math problem

 

[Spider-Bite]

sorry it took so long. it's a brand new scanner I never used before.

 

[Catman]

Oh God! It's high school and college Algebra all over again.

 

[JStorm]

D.

Shall I explain?

Edit: It gives you the answer. Why can't you do this?

 

[Spider-Bite]

D.

Shall I explain?

Edit: It gives you the answer. Why can't you do this?

I'm not sure how they got the answer. I feel like an idiot but I really need to learn it.

 

[Catman]

Why can't you do this?

LMFAO t:

 

[Catman]

I feel like an idiot but I really need to learn it.

It's okay, dude. I was a genius then I'd walk into math class and I would feel like the biggest moron on the planet.

 

[JStorm]

I'm not sure how they got the answer. I feel like an idiot but I really need to learn it.

Calm down. Take a break, and come back in another five minutes. I'll break it down as easy as I can for you.

 

[Spider-Bite]

Calm down. Take a break, and come back in another five minutes. I'll break it down as easy as I can for you.

thank you very much.

 

[GoldenAgeHero]

dude you can't do college algebra? that was an easy problem. but don't worry i could'nt figure out most of the problems on the ACT but i still got a high enough score. but that was really simple math problem.

post another one.

 

[Spider-Bite]

dude you can't do college algebra? that was an easy problem. but don't worry i could'nt figure out most of the problems on the ACT but i still got a high enough score. but that was really simple math problem.

post another one.

I got a 56%, on a practice the other day. I don't know what the average is, or what passing is, but I'm sure my score isn't either of them. I'm going to try and study my ass off for the next few days and hopefully take it and get a high score within the next week. I know my main problem was math. I don't even know how I got through math in high school, because I sure as heck didn't bother to learn anything.

 

[JStorm]

First step, forget about the negative sign. Had it been in both numbers, then it would be common and important. Forget it.

Second, there is an 8 and a 12. The GCF of these two numbers is 4. To make it easier, write an 8 and a 12 on a piece of paper. Under the numbers, write the numbers that multiply to make 8 or 12. DO THEM SEPERATELY. For example, 8 = 1 x 8 and 12 = 1 x 12 and so on.

Third, there is other common factors in this binomial. Those common factors are known as exponets and variables. The exponets are the little "2's" above the x and Y. The variables and the x's and y's. UNDERSTAND THAT A 2 ABOVE ANY VARIABLE MEANS TWO VARIABLES. In other words, x(with a two over it) = x times x. So, essentianlly, you have 8xxy and 12xyy.

Fourth, look at the entire binomial. What is commom? What is not? Take out the common factors and leave what's left in the parentheses.

Like so: 4xy(-2x + 3y)
The 4xy is taken out becuse when you distribute the 4xy into the binomial you just factores the 4xy times -2x = -8(x squared)y + 3x(ysquared)

Sorry about having to write "square."

Do you understand?

 

[Lackey]

first off thanks for taking your time here.

I think so, but I just realized that the math problem didn't show up here the way it was supposed to, so I'm scanning it real quick to post it. give me a second.

a common factor is a number that your starting numbers are divisible by... 8 and 12 are both divisible by 4. Usually, in problems like this, you're looking for the greatest common factor (GCF) -- the largest number that they are divisible by.

for example, the greatest common factor of 12 and 30 is 6 because 6 is the largest number that will go into both 12 and 30.


so, if you have 8 and 12 and you 'factor out' 4, then you're left with 2 and 3.


the other part might seem confusing at first, but it works the same way when you just take it one part at a time...

x^2 and x have a greatest common factor of x
y and y^2 have a greatest common factor of y

so you end up with 4xy being factored out of the problem.

I think you can understand why it is 4xy and not -4xy because only the first part in the original problem is negative, not both. So that when you work the problem backwards...if you try working out A, B, C, and D... only D will give you the original problem.

maybe JStorm can give you more details.

 

[GoldenAgeHero]

i dunno, spider-bite. i don't want to bring you down or anything, but i f you can't understand a problem like this, the ACT is going to pretty much murder you! you should've gone to a remedial class or something.

 

[JStorm]

a common factor is a number that your starting numbers are divisible by... 8 and 12 are both divisible by 4. Usually, in problems like this, you're looking for the greatest common factor (GCF) -- the largest number that they are divisible by.

for example, the greatest common factor of 12 and 30 is 6 because 6 is the largest number that will go into both 12 and 30.


so, if you have 8 and 12 and you 'factor out' 4, then you're left with 2 and 3.


the other part might seem confusing at first, but it works the same way when you just take it one part at a time...

x^2 and x have a greatest common factor of x
y and y^2 have a greatest common factor of y

so you end up with 4xy being factored out of the problem.

I think you can understand why it is 4xy and not -4xy because only the first part in the original problem is negative, not both. So that when you work the problem backwards...if you try working out A, B, C, and D... only D will give you the original problem.

maybe JStorm can give you more details.

If you can't understand after Lackey and I just spelled it out for you, you need to get a tutor.

I'm not being harsh; this is just terribly hard to explain over the net.

BTW, good job, Lackey!

 

[Lackey]

i dunno, spider-bite. i don't want to bring you down or anything, but i f you can't understand a problem like this, the ACT is going to pretty much murder you! you should've gone to a remedial class or something.

well, it depends how high of an ACT score he's going for and if the math score matters all that much to what he's going into

 

[Spider-Bite]

First step, forget about the negative sign. Had it been in both numbers, then it would be common and important. Forget it.

Second, there is an 8 and a 12. The GCF of these two numbers is 4. To make it easier, write an 8 and a 12 on a piece of paper. Under the numbers, write the numbers that multiply to make 8 or 12. DO THEM SEPERATELY. For example, 8 = 1 x 8 and 12 = 1 x 12 and so on.

Third, there is other common factors in this binomial. Those common factors are known as exponets and variables. The exponets are the little "2's" above the x and Y. The variables and the x's and y's. UNDERSTAND THAT A 2 ABOVE ANY VARIABLE MEANS TWO VARIABLES. In other words, x(with a two over it) = x times x. So, essentianlly, you have 8xxy and 12xyy.

Fourth, look at the entire binomial. What is commom? What is not? Take out the common factors and leave what's left in the parentheses.

Like so: 4xy(-2x + 3y)
The 4xy is taken out becuse when you distribute the 4xy into the binomial you just factores the 4xy times -2x = -8(x squared)y + 3x(ysquared)

Sorry about having to write "square."

Do you understand?

I think so, but I'm not sure. I was gonna test myself by giving myself a problem to solve, but I'm afraid that by doing that I might be cheating even if I don't realize it. Could you give me a problem like that to try and solve and tell me if I get it correct?

by the way i really appreciate your taking the time to do this.