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2 numeros que multiplicados me den -21 y sumados -22

Guest Jul 2, 2017
 #1
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+3

 

2 numbers that multiplied give me -21 and added -22

 

Let x, y  be the numbers

 

So

 

xy  =  -21     (1)

x + y  =  -22  →  y  = -22 - x      (2)

 

 

Subbing (2)  into (1), we have that

 

x ( -22 - x)  =  -21   simplify

 

-22x - x^2  = -21   add 21 to both sides

 

22x + x^2  = 21  subtract 21 from both sides

 

22x + x^2 - 21  = 0   rearrange

 

x^2 + 22x - 21  = 0

 

We can use the quadratic formula to solve this

 

WoframAlpha  gives the two solutions for x  as :

 

-11 + √142    and    -11 - √142

 

Choosing either for x will mean that y will be the other solution

 

 

 

cool cool cool

CPhill  Jul 2, 2017

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