CPhill

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 #1
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+5

Very nice, zacismyname   !!!   ....you're correct.....this is a good one  !!!

We could also do it with one varable from the start :

Let Charlotte's age be x  and Emily's age be 2x

So we have

(2x - 4)(x - 4) = 30

2x^2 - 12x + 16 = 30

2x^2 - 12x - 14 = 0

x^2 - 6x - 7  = 0

(x - 7) (x + 1) = 0      so x = 7 or  x = -1   .....reject  - 1  .....

So.....x = 7  = Charlotte's age     and 2(7)  = 14 = Emily's age

Just as you found  !!!!

 

  

03.05.2015