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One of the roots of the equation kx^2 - 2x - 3 = 0 is -3. Find the value of k.

Guest Mar 19, 2017
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 #1
avatar+26241 
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We must have:  (x + 3)(kx - a) = 0

 

So:  kx2 + (3k-a)x - 3a = 0. 

 

Compare term by term with kx2 -2x - 3 = 0

 

Clearly a = 1, so 3k - 1 = -2

 

3k = -1

 

k = -1/3

 

.

Alan  Mar 19, 2017
 #2
avatar+10614 
+1

Another method: SUbstitute in -3 fo 'x'  and solve for 'k'

k(9) + 6-3 = 0

k(9) = -3

k = -3/9 = -1/3

ElectricPavlov  Mar 19, 2017

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