+0  
 
0
698
2
avatar

I cannot figure out how to do this

Solve for k

-1/3 is a solution

 May 19, 2016
edited by Guest  May 19, 2016

Best Answer 

 #1
avatar
+5

Solve for k:
k x^2-13 x = 5

 

Add 13 x to both sides:
k x^2 = 13 x+5

 

Divide both sides by x^2:
Answer: |  k = 13/x+5/x^2

 

P.S. You cannot get a numerical value for k, because you have 2 unknowns, x and k. You can only solve for k in terms of x.

 May 19, 2016
 #1
avatar
+5
Best Answer

Solve for k:
k x^2-13 x = 5

 

Add 13 x to both sides:
k x^2 = 13 x+5

 

Divide both sides by x^2:
Answer: |  k = 13/x+5/x^2

 

P.S. You cannot get a numerical value for k, because you have 2 unknowns, x and k. You can only solve for k in terms of x.

Guest May 19, 2016
 #2
avatar+33653 
+5

k*x^2 -13*x - 5 = 0

 

Use the quadratic formula to obtain solutions:  x1 = (13 - sqrt(20*k + 169))/(2k)  and x2 = (13 + sqrt(20*k + 169))/(2k)

 

Only x1 could be -1/3, so:

 

(13 - sqrt(20*k + 169))/(2k) = -1/3

 

3*(13 - sqrt(20*k + 169)) = -2k

 

39 = 3*sqrt(20k + 169) - 2k

 

39 + 2k = 3*sqrt(20k + 169)

 

Square both sides:

 

39^2 + 4*39*k + 4k^2 = 9*(20k + 169)

 

4k^2 - 24k = 0

 

k(k - 6) = 0

 

k = 0 or k = 6  (Only the k = 6 solution keeps the original equation as a quadratic).

 May 19, 2016

1 Online Users