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Find all values of $x$ such that $\dfrac{x}{x+4} = -\dfrac{9}{x+3}$. If you find more than one value, then list your solutions in increasing order, separated by commas.

Guest Dec 30, 2017

Best Answer 

 #1
avatar+17736 
+2

x / (x + 4)  =  -9 / (x + 3)                                            Numbers that cannot be answers:  -4, -3

Cross multiply:

x(x + 3)  =  -9(x + 4)

x2 + 3x  =  -9x - 36

x2 + 3x + 9x + 36  =  0

x2 + 12x + 36  =  0

(x + 6)(x + 6)  =  0

x  =  -6

geno3141  Dec 30, 2017
 #1
avatar+17736 
+2
Best Answer

x / (x + 4)  =  -9 / (x + 3)                                            Numbers that cannot be answers:  -4, -3

Cross multiply:

x(x + 3)  =  -9(x + 4)

x2 + 3x  =  -9x - 36

x2 + 3x + 9x + 36  =  0

x2 + 12x + 36  =  0

(x + 6)(x + 6)  =  0

x  =  -6

geno3141  Dec 30, 2017

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