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Dec 30, 2020
 #1
avatar+122 
-1

Before we start, note that in the problem 125 divided by 8, the numbers are defined as follows:

125 = dividend
8 = divisor

 

Step 1:
Start by setting it up with the divisor 8 on the left side and the dividend 125 on the right side like this:

       

  8⟌125


Step 2:
The divisor (8) goes into the first digit of the dividend (1), 0 time(s). Therefore, put 0 on top:
 

    0  

  8⟌125


Step 3:
Multiply the divisor by the result in the previous step (8 x 0 = 0) and write that answer below the dividend.
 

    0  

  8⟌125

   0  


Step 4:
Subtract the result in the previous step from the first digit of the dividend (1 - 0 = 1) and write the answer below.
 

    0  

  8⟌125

   -0  

    1  


Step 5:
Move down the 2nd digit of the dividend (2) like this:
 

    0  

  8⟌125

   -0  

    12 


Step 6:
The divisor (8) goes into the bottom number (12), 1 time(s). Therefore, put 1 on top:
 

    01 

  8⟌125

   -0  

    12 


Step 7:
Multiply the divisor by the result in the previous step (8 x 1 = 8) and write that answer at the bottom:
 

    01 

  8⟌125

   -0  

    12 

     8 


Step 8:
Subtract the result in the previous step from the number written above it. (12 - 8 = 4) and write the answer at the bottom.
 

    01 

  8⟌125

   -0  

    12 

   - 8 

     4 


Step 9:
Move down the last digit of the dividend (5) like this:
 

    01 

  8⟌125

   -0  

    12 

   - 8 

     45


Step 10:
The divisor (8) goes into the bottom number (45), 5 time(s). Therefore put 5 on top:
 

    015

  8⟌125

   -0  

    12 

   - 8 

     45


Step 11:
Multiply the divisor by the result in the previous step (8 x 5 = 40) and write the answer at the bottom:
 

    015

  8⟌125

   -0  

    12 

   - 8 

     45

     40


Step 12:
Subtract the result in the previous step from the number written above it. (45 - 40 = 5) and write the answer at the bottom.
 

    015

  8⟌125

   -0  

    12 

   - 8 

     45

   - 40

      5


You are done, because there are no more digits to move down from the dividend.

The answer is the top number and the remainder is the bottom number.

Therefore, the answer to 125 divided by 8 calculated using Long Division is:

15
5 Remainder

Dec 30, 2020
 #2
avatar
0
Dec 30, 2020
 #1
avatar+129840 
+1

y  = x   - 1/x

 

y =  [ x^2 -1 ] / x

 

xy   =  x^2    - 1

 

Trying to get x by itself  and then "swap" x  and  y is sticky

 

Here's one approach   by completing the  square on  x

 

yx  =  x^2  - 1          rearrange as

 

x^2  - yx     - 1    =   0       complete the square

 

Take 1/2  of y  =  y/2   square it  = y^2/4   add to both  sides

 

x^2  - yx   + (y^2/4)   =  1  + (y^2/4)       the left side  factors as

 

( x - y/2)^2  = ( 4 + y^2) / 4

 

x - y/2  =  ± √(4 + y^2)  / 2

 

x =  ± √(4 + y^2)  /  2  + y/2

 

x  =   [ y ± √ (4 + y^2) ]   / 2      "swap"  x and  y

 

y =  [ x ± √ (4 + x^2 ) ]  / 2   =    the "inverse"

 

Note  that  if  x  =  1   in the  first function, then  y   =  0

 

So   the point    ( 0, 1)   should  be  on the  "inverse" graph...so

 

1  =  [ 0 ± √ [ 4 + 0  ]   ] / 2

 

1  = ± √4/2

 

1  =  ±1

 

This is  only  true  if we  take the positive root

 

So.....  x  - 1/x     has no inverse   on   (-inf, 0)  U (0, inf)  because  we don't get a unique point for the "inverse"

 

However....if we restrict the domain of  g (x) to    (0, inf)    then  the inverse  becomes

 

y =  [ x +  √ [ 4  + x^2 ]   ]  /  2

 

Now.....note if   x =   2  in  g(x)   then   g(2)  =  3/2

 

And the point  ( 2,3/2) is  on g

 

So....the point   (3/2 , 2)   should be  on the  inverse   of  g

 

So

 

2 =   [ 3/2 +  √ [ 4 + (3/2)^2 ]   ]/  2

 

4 =  3/2  +    √ [ 4 + 1.5^2 ]   

 

4 =  3/2  +  √ [ 4 + 2.25  ]   

 

5/2  =  √(6.25  

 

2.5   = 2.5      which is true

 

So we  have an inverse if we  restrict the  domain  to  (0, inf)

 

Also.....look at the  graph here  for  x  -1/x

 

https://www.desmos.com/calculator/g4o70vl223

 

This  graph  does not pass the horizontal line test  ( a requirement for an inverse)

 

However....if we  restrict the  domain  to   (0, inf)   we will have a  graph that will pass the horizontal line test,  and so, it will have an inverse

 

cool cool cool

Dec 30, 2020

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