# Need to find the values of a and b

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• Jan 5th 2013, 05:38 AM
khorne55
Need to find the values of a and b
(z-2)(z^2+az+b)=z^3-4z^2+6z-4 a,b are an element of Z.

Honestly have no idea how to solve this all help welcome. Thanks
• Jan 5th 2013, 07:13 AM
earboth
Re: Need to find the values of a and b
Quote:

Originally Posted by khorne55
(z-2)(z^2+az+b)=z^3-4z^2+6z-4 a,b are an element of Z.

Honestly have no idea how to solve this all help welcome. Thanks

1. Expand the LHS:

$(z-2)(z^2+az+b) = z^3 + z^2(a - 2) + z(b - 2a) - 2b$

2. Now compare the coefficients of the RHS:

$\begin{array}{lcr}a-2&=&-4 \\ b-2a&=&6 \\ -2b&=&-4 \end{array}$

3. Solve the system of equations for a and b.
• Jan 5th 2013, 08:48 AM
khorne55
Re: Need to find the values of a and b
Thanks a lot ! a= -2 and b =2 That clears out the whole situation. I am really grateful for your help!