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avatar+11912 

I have a confusion becoz of which I always lose marks as I have a very cunning math teacher and she said if even one mistake occurs she will give a zero for the whole question so pls help me solve this confusion!

 

i have a confusion in plus minus like if a question is this 

 

-3x + 5x then I think the answer will be 8x becoz my tuition teacher once told me that if any sign is bigger then we will follow it and also put the same sign like here + is bigger so I've applied it!

is this correct becoz once I did it and lot marks?

another confusion is that suppose a question is -3x + 5x so I think the answer would be 2x becoz I remember when I told my tuition teacher about the marks she said in this type of question we will subtract and then put the sign which is bigger!

 

is this correct becoz once I didn't it and lost marks???

now pls tell me which one should I apply I don't want to lose sooooo many marks! I need serious help!

 

CPhill pls save my life.......

 

 Jan 18, 2015

Best Answer 

 #1
avatar+128732 
+10

Let me tell you a foolproof method for dealing with unlike signs....this ALWAYS works..

Suppose we have  -3x + 5x...

First...."forget" the signs...so we have  3x and 5x

Take the "bigger" thing  and subtract the "smaller" thing...so we have

5x - 3x  = 2x

Now...what was the sign on the "bigger" thing??   a "+", right??  ..   so that's the sign we write with our  answer....  so... -3x + 5x = +2x

So, for example...what if we had -29x + 15x  ??

First....forget the signs

Take the "bigger" thing  29x  and subtract the "smaller" thing...so we have

29x - 15x   = 14x

Now....we ask ourselves the question....what was the sign on the "bigger" thing??

It was a  " -".....right??

So....that's the sign we use in our answer   =  -14x   !!!

Does that help??

 

Just for the heck of it...try these two and let me know what you get...remember if there is no sign, it's assumed to be  "+"

39y - 10y

- 45x  + 13x

 

 Jan 18, 2015
 #1
avatar+128732 
+10
Best Answer

Let me tell you a foolproof method for dealing with unlike signs....this ALWAYS works..

Suppose we have  -3x + 5x...

First...."forget" the signs...so we have  3x and 5x

Take the "bigger" thing  and subtract the "smaller" thing...so we have

5x - 3x  = 2x

Now...what was the sign on the "bigger" thing??   a "+", right??  ..   so that's the sign we write with our  answer....  so... -3x + 5x = +2x

So, for example...what if we had -29x + 15x  ??

First....forget the signs

Take the "bigger" thing  29x  and subtract the "smaller" thing...so we have

29x - 15x   = 14x

Now....we ask ourselves the question....what was the sign on the "bigger" thing??

It was a  " -".....right??

So....that's the sign we use in our answer   =  -14x   !!!

Does that help??

 

Just for the heck of it...try these two and let me know what you get...remember if there is no sign, it's assumed to be  "+"

39y - 10y

- 45x  + 13x

 

CPhill Jan 18, 2015
 #2
avatar+11912 
+5

Thank you so much CPhill. I get and I'm answering your two questions!

 

the answer to the first one is 29y and second one is -32 x , am I right?

 Jan 18, 2015
 #3
avatar+128732 
+5

Those answers are right on, rosala....easy as falling off a log, huh ???

 

 Jan 18, 2015
 #4
avatar+11912 
+5

Nah, I don't fall off a log so easily but I do slip on the stairs easily! Lol! 

 Jan 18, 2015

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