Algebra questions

[Deleted]

This seems like too simple a question, but...

-(X-3)  -  2(x-4) 

is the next line   - x + 3 - 2x - 8    Or     - x + 3 - 2x + 8. ... And why... Thanks.

[Deleted]

Sept 6, 2013 11:34:40 GMT -5 oped said:

This seems like too simple a question, but...

-(X-3)  -  2(x-4) 

is the next line   - x + 3 - 2x - 8    Or     - x + 3 - 2x + 8. ... And why... Thanks.

+8
distribute the negative to the x and the -3 then distribute the -2 to the x and the -4

it's the same as + (-2)(x-4)

[Deleted]

Been a long time since I have this, but I vote for +8.  Because that seems right to me.

[Deleted]

The second.

The (x-4) is a group. If you distribute -2 to the x, you have to do the same to the -4.

That's what I recall from ages ago anyway.

[Regis]

-x+3-2x+8 because two negatives make a positive.

And try this:  Substitute the number 5 for x
If you use the original equation you get -(5-3) - 2(5-4) or -2-2=-4
If you use -x+3-2x-8 you get -5+3-10-8= -20
If you use -x+3-2x+8 you get -5+3-10+8=-4 (same answer as above)

[Deleted]

Ok. I do need to distribute it as a negative two, and not think of it as minus 2 (x-4)s... 

Just checking! Thanks.

[Deleted]

Sept 6, 2013 11:42:36 GMT -5 Regis said:

-x+3-2x+8 because two negatives make a positive.

And try this:  Substitute the number 5 for x
If you use the original equation you get -(5-3) - 2(5-4) or -2-2=-4
If you use -x+3-2x-8 you get -5+3-10-8= -20
If you use -x+3-2x+8 you get -5+3-10+8=-4 (same answer as above)

Duh, that's what I needed. I'm being dense today. Thanks again. 

[Regis]

Sept 6, 2013 11:46:22 GMT -5 oped said:

Sept 6, 2013 11:42:36 GMT -5 Regis said:

-x+3-2x+8 because two negatives make a positive.

And try this:  Substitute the number 5 for x
If you use the original equation you get -(5-3) - 2(5-4) or -2-2=-4
If you use -x+3-2x-8 you get -5+3-10-8= -20
If you use -x+3-2x+8 you get -5+3-10+8=-4 (same answer as above)

Duh, that's what I needed. I'm being dense today. Thanks again. 

It's Friday.  Everybody's brain cells are toast.

[Deleted]

Lol. I like to make sure when I'm explaining to him why/how that he can 'break it down' to its smallest components, prove why it is that way, and i just couldn't think how today. Bluh.. But you give it to me...  

[Formerly SK]

WOW I got it right!  Perhaps I can help my kids with their math homework after all! 

[Deleted]

What I was really trying to do was bring it into a real world, story problem and failing. 

But, 

... If I had a large quantity of donuts and gave two groups a small quantity of donuts, I'd have to subtract what I gave them, but if not all of those were eaten, I'd have to ADD back in those that weren't. 

Ie. 500 donuts - 2(50 donuts I gave them - 4 not eten that I returned) the problem would be 500- 100 + 8... Whew... 

Lol. 

[Phoenix84]

The second

You distribute the number ahead of the perenthises to every factor inside the perenthises.  Essentially you just multiply them.  In the first case you have a -1 outside the perenthises, so -1 * X = -X and -1 * -3 = +3, because multiplying two negative numbers yields a positive number.  For the second term, multiplying -2 * X = -2X and doing -2 * -4 yields +8.

[Phoenix84]

Sept 6, 2013 13:11:33 GMT -5 oped said:

What I was really trying to do was bring it into a real world, story problem and failing. 

But, 

... If I had a large quantity of donuts and gave two groups a small quantity of donuts, I'd have to subtract what I gave them, but if not all of those were eaten, I'd have to ADD back in those that weren't. 

Ie. 500 donuts - 2(50 donuts I gave them - 4 not eten that I returned) the problem would be 500- 100 + 8... Whew... 

Lol. 

If you wanted to set that up, you could do it this way.

X = # of original doughnuts

Y = # of doughnuts given out

Z = # of doughnuts not eaten in a given group

D = # of groups of doughnuts given out.

So the formula would be X - (Y-Z). 

ETA LOL the D showed up as a smiley.

[kcladyjane]

Wow I just realized I totally forgot how to do algebra.  Hmmmph - who cares...I don't use that in the real word.  Well not in "my" real world.

[Deleted]

one train leaves Chicago at 5:00 going 65 mph and making 3 20 minutes stops.

one train leaves New York at 1:00 going 75 mph a makes 1 30 minute stop.  

When do you buy your plane ticket?

[Deleted]

Basically I wanted a concrete rationale for why distribution of the -2 was required... 

[justme]

Sept 6, 2013 11:36:58 GMT -5 @singlemominmd said:

Sept 6, 2013 11:34:40 GMT -5 oped said:

This seems like too simple a question, but...

-(X-3)  -  2(x-4) 

is the next line   - x + 3 - 2x - 8    Or     - x + 3 - 2x + 8. ... And why... Thanks.

+8
distribute the negative to the x and the -3 then distribute the -2 to the x and the -4

it's the same as + (-2)(x-4)

When I tutored I did that trick. Also changed -(x-3) to (-1)(x-3).

Some people would read it "minus 2 times parenthesis x-4 parenthesis" and therefore not carry the negative into the (x-4), but the simple change made them read it "plus negative two times parenthesis x-4 parenthesis" and made all the difference.

[kittensaver]

Sept 6, 2013 13:35:15 GMT -5 ArchietheDragon said:

one train leaves Chicago at 5:00 going 65 mph and making 3 20 minutes stops.

one train leaves New York at 1:00 going 75 mph a makes 1 30 minute stop.  

When do you buy your plane ticket?

After you've downed two rounds of margaritas.

[Otto the Orange]

Did you remember to carry the one? 

[Jake 48]

Sept 6, 2013 13:35:15 GMT -5 ArchietheDragon said:

one train leaves Chicago at 5:00 going 65 mph and making 3 20 minutes stops.

one train leaves New York at 1:00 going 75 mph a makes 1 30 minute stop.  

When do you buy your plane ticket?

I believe you have to follow the "order of operations"

exponents and roots
multiplication and division
addition and subtraction

and there are some exceptions

[zibazinski]

This is why I took two years of geometry and only one year of algebra. It's still MATH to me! When they told me algebra two came after geometry one, I stood my ground and said not in my universe!

[Otto the Orange]

Sept 6, 2013 13:35:15 GMT -5 ArchietheDragon said:

one train leaves Chicago at 5:00 going 65 mph and making 3 20 minutes stops.

one train leaves New York at 1:00 going 75 mph a makes 1 30 minute stop.  

When do you buy your plane ticket?

Plane tickets are cheapest during "shoulder season"