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Jun 3, 2021
 #5
avatar+514 
+1
Jun 3, 2021
 #2
avatar+118630 
0

CPhill has continued this here:       (Thanks Chris)

 

https://web2.0calc.com/questions/help-me-melody_2

 

I will just copy CPhill's answer over, it is probably easier:

 

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

 

2 out of 5 students voted for John. The other students voted for Tommy. If 9 students voted for Tommy, how many students voted in all?

 

In every group  of 5,  2 voted for John and 3 voted for Tommy

 

So

 

2/3  of Tommy's vote  = Jonh's vote

 

(2/3) (9)  =   6  voted for John

 

9 +  6   =    15   voted

Jun 3, 2021
 #1
avatar+129643 
+2

sqrt  [( x + h)^2  + 9 ]   -  sqrt  [ x^2  + 9]

_________________________________

                              h

 

sqrt  [  x^2  + 2xh  + h^2   +  9 ]  -  sqrt  [ x^2 + 9]

__________________________________________   

                                    h 

 

Multiply top / bottom  by    sqrt  [ x^2  + 2xh  + h^2 + 9 ]  +  sqrt [  x^2 + 9 ]

 

               x^2  + 2xh   + h^2  + 9   - x^2 - 9

________________________________________     =

       h   [ ( sqrt x^2 + 2xh + h^2 + 9)  +  (sqrt (x^2 + 9) ] 

 

 

          2xh  + h^2

______________________________________    =       

 h   [ ( sqrt x^2 + 2xh + h^2 + 9)  +  (sqrt (x^2 + 9)  ]

 

 

                    h (2x + h)

_______________________________________  = 

 h   [ ( sqrt x^2 + 2xh + h^2 + 9)  +  (sqrt (x^2 + 9)  ]

 

 

                      2x  +  h

______________________________________           let   h approach  0     and we have

    [ ( sqrt x^2 + 2xh + h^2  + 9)  +  (sqrt (x^2 + 9)  ]

 

 

                         2x

_______________________________________      =

     sqrt (x^2 + 9)   +  sqrt (x ^2  + 9)

 

 

                          2x

_________________________________  =

            2sqrt (x^2 + 9)

 

 

                                         x

                         ____________________

                               sqrt (x^2 + 9)

 

If you take Calculus.....you  will   learn  that   the  derivative of  (x^2 + 9)^(1/2)  =

 

(1/2)  (2x)  / ( (x^2 + 9)^(1/2)  =       x   /  sqrt ( x^2 + 9)        =   our result  !!!!

 

 

cool cool cool

Jun 3, 2021
 #1
avatar+514 
+2
Jun 3, 2021

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