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If z=9/2 is a solution of the equation 2z²+kz-30=6, find:

 

a) the value of k

b) the other solution of the equation

 

I appreciate any form of help, thank youlaugh

Guest Sep 5, 2017

Best Answer 

 #1
avatar+26752 
+2

a)  Substitute 9/2 for z in the equation:

 

2*(9/2)2 + k*9/2 - 30 = 6

 

81/2 + 9k/2 = 36

81 + 9k = 72

9k = -9

k = -1

 

b) Use this value of k in the original equation:

2z2 - z -30 = 6

2z2 - z -36 = 0

z2 - z/2 -18 = 0

(z + 4)(z - 9/2) = 0

 

The other solution is therefore z = -4

.

Alan  Sep 5, 2017
 #1
avatar+26752 
+2
Best Answer

a)  Substitute 9/2 for z in the equation:

 

2*(9/2)2 + k*9/2 - 30 = 6

 

81/2 + 9k/2 = 36

81 + 9k = 72

9k = -9

k = -1

 

b) Use this value of k in the original equation:

2z2 - z -30 = 6

2z2 - z -36 = 0

z2 - z/2 -18 = 0

(z + 4)(z - 9/2) = 0

 

The other solution is therefore z = -4

.

Alan  Sep 5, 2017

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