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December 21st, 2010, 10:26 PM   #1
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Matrix question (confusing)

Given that A=( ) a11=2, a12=2, a21=3, a22=-1, (it is a matrix, sorry I can't type matrix in word) find A^2 and A^3.


If f(x)= x^3-3x^2-2x+4, find f(A). If g(x)=x^2-x-8, find g(A).


I have solved many kinds of problem in matrix, but this confusing me a lot. I dunno how to do. I only can find A^2 and A^3. Please help me step by step.
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December 22nd, 2010, 04:25 AM   #2
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Re: Matrix question (confusing)

help me !!!
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December 22nd, 2010, 06:40 AM   #3
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To add matrices (of the same size), add corresponding elements. To multiply a matrix by a constant, multiply each element of the matrix by the constant.

I suggest interpreting "+ 4" and "- 8" as "+ 4I" and "- 8I", where I is the identity matrix (having 1 as each element of the main diagonal, and zero for all the other elements).

Hence g(A) = A - A - 8I =

Can you complete the answer by finding f(A) now?
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December 23rd, 2010, 05:58 AM   #4
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Re: Matrix question (confusing)

I don't really understand. Anyone else can help?
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December 23rd, 2010, 08:01 AM   #5
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Can you be more specific? For example, do you know how matrix multiplication is done?
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December 30th, 2010, 08:28 PM   #6
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Re: Matrix question (confusing)

Hi,

Dear hoyy1kolko, I understand your problem. I suggest this site for your problems. This is an easy calculation site for all math problems.
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