Questions   
Sort: 
 #1
avatar+676 
+8

To answer this question you will need to break down this equation.

First of all lets try and simplify all that can be simplified.

$${\frac{{\mathtt{1}}}{{\mathtt{x}}}}{\mathtt{\,\small\textbf+\,}}{\frac{{\mathtt{x}}}{{\mathtt{x}}}}{\mathtt{\,\small\textbf+\,}}{\mathtt{2}} = {\mathtt{1}}$$

First of all we can see a fraction that can be simplified. That is ofcourse, X Over X. Any number, if the Numerator and Denominator is identical, then it will always equal to 1. So being that, we will substitute X over X with 1.

$${\frac{{\mathtt{1}}}{{\mathtt{x}}}}{\mathtt{\,\small\textbf+\,}}{\mathtt{1}}{\mathtt{\,\small\textbf+\,}}{\mathtt{2}} = {\mathtt{1}}$$ 

Let us move over some numbers across the = sign.

$${\frac{{\mathtt{1}}}{{\mathtt{x}}}} = {\mathtt{1}}{\mathtt{\,-\,}}{\mathtt{2}}{\mathtt{\,-\,}}{\mathtt{1}}$$

Lets solve that:

$${\frac{{\mathtt{1}}}{{\mathtt{x}}}} = -{\mathtt{2}}$$

Now we must eradicate the denominator. To do that we will multiply both sides by x.

$${\frac{{\mathtt{1}}}{{\mathtt{x}}}}{\mathtt{\,\times\,}}{\mathtt{x}} = {\mathtt{\,-\,}}\left({\mathtt{2}}{\mathtt{\,\times\,}}{\mathtt{x}}\right)$$

Lets solve that!

$${\frac{{\mathtt{1}}}{{\mathtt{x}}}}{\mathtt{\,\times\,}}{\mathtt{x}} = {\mathtt{\,-\,}}\left({\mathtt{2}}{\mathtt{\,\times\,}}{\mathtt{x}}\right) \Rightarrow {\mathtt{x}} = {\mathtt{\,-\,}}{\frac{{\mathtt{1}}}{{\mathtt{2}}}} \Rightarrow {\mathtt{x}} = -{\mathtt{0.5}}$$

We have jumped a step, however, you should be able to see what has been done.

x=-0.5

Lets substitute that in!

$${\frac{{\mathtt{1}}}{-{\mathtt{0.5}}}}{\mathtt{\,\small\textbf+\,}}{\frac{\left(-{\mathtt{0.5}}\right)}{-{\mathtt{0.5}}}}{\mathtt{\,\small\textbf+\,}}{\mathtt{2}} = {\mathtt{1}}$$

Lets solve it now and see if it work!

$${\frac{{\mathtt{1}}}{-{\mathtt{0.5}}}} = -{\mathtt{2}}$$

$${\frac{\left(-{\mathtt{0.5}}\right)}{-{\mathtt{0.5}}}} = {\mathtt{1}}$$

$${\mathtt{\,-\,}}{\mathtt{2}}{\mathtt{\,\small\textbf+\,}}{\mathtt{1}}{\mathtt{\,\small\textbf+\,}}{\mathtt{2}} = {\mathtt{1}}$$

Is it correct?

Yes!

Therefore $${\mathtt{x}} = -{\mathtt{0.5}}$$

.
May 22, 2014
 #2
avatar+118723 
+10

Good question!

Two minus make a plus ONLY

1) if they are so close together that you can put a circle around them and there is nothing else in  the circle.

Think of it like this if you want

Negative numbers are cold numbers.  Like -30degrees would be very cold wouldn't it?

and Positive numbers are hot numbers.  An oven might be 180degrees. There is an invisible + in front of the 180.

So 15--2 means you are taking away cold - so it must get hotter

15--2=15+2=17

2) If you are multiplying or dividing

--------------------------------------------------------------------

NOW if you are adding or subtracting positive and negative numbers then you need to think about a number line.

10+3 means you start at 10 and go 3 places in the positive direction = 13

10-3 means you start at 10 and go 3 places in the negative direction = 7

Just continue this method with trickier negative numbers

-3-8 means you start at -3 and go 8 places in the negative direction = -11

OR to put it another way.  It is -3 degrees and it gets 8 degrees COLDER = -11 degrees

So lets look at your question

-7+-8 = If you add cold it gets colder so the question becomes

-7-8     Now if it is -7 degrees that pretty cold and you take away 8 degrees, it is going to get even colder! So the answer must be more negative.  

Start at -7 on the number line and go 8 places in the negative direction.  The answer is -15

I don't know why I am writing all this I am sure that I have done it before as a post to keep.  Not to worry.

Here is a number line that might help you. You'll have to add the negative numbers in yourself.

Here is a site that might also help.   

http://www.mathsisfun.com/positive-negative-integers.html

May 22, 2014

0 Online Users