# Homework Help: Matrices trouble, making a,b,c no sol, a unique, and infin solutions

1. Sep 26, 2005

### mr_coffee

Hello everyone. I'm having troubles understanding if i'm doing this right.
I have the matrix
$$\left( {\begin{array}{*{20}c} 2 & {-3} & {-3} & a \\ {-1} & 1 & 2 & b \\ 1 & {-3} & 0 & c \\ \end{array} } \right)$$

I row reduced it to:
$$\left( {\begin{array}{*{20}c} 2 & {-3} & {-3} & a \\ 0 & {-1} & 1 & 2b+a \\ 0 & {0} & 0 & {-3b-2a+c} \\ \end{array} } \right)$$

I'm suppose to find, In each case find if possible conditions on the numbers a, b, and c that the given syhstem has no solution, a unique solution, or infintnety many s9lutions. So would i let b = 0, a = 0 and c equal 0 to make it have an infinit many solutions. and then let a, b and c be any number so the expression: -3b-2a+c wil not equal 0, so 0 = 4, no solution. How would i find a unique solution? if the last row is already 0 = -3b-2a+c? thanks!

2. Sep 26, 2005

### TD

In order to have at least one solution, the last row cannot by all 0 and a non-zero final element. So in order to have solutions, you have to let $-3b-2a+c = 0$.

Can you take it from here?

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