Question

For which values of k does the system of linear equations have zero, one, or an infinite number of solutions? [Note: not all three possibilities need occur.] (If the answer is an interval of numbers, enter your answer using interval notation. If an answer does not exist, enter DNE.) 3x1 − x2 = 2 9x1 − 3x2 = k

Answer 1

Answer:

The system has an infinite solution at k = 6, otherwise for any value of k, it has zero solution.

Step-by-step explanation:

Consider the system of linear equations:

$3x_{1} -x_{2}=2\;\;\;\;\;\;(1)\\ 9x_{1} -3x_{2}=k\;\;\;\;\;(2)$

The system of linear equations can have zero, one, or an infinite number of solutions:

simplify equation (1):

$x_{2}=3x_{1} -2$

substitute in equation (2), we get

$9x_{1} -3(3x_{1}-2)=k\\9x_{1} -9x_{1}+6=k\\0+6=k$

we cannot find the value of $x_{1}$ and $x_{2}$.

so, there is no solution.

Multiply the equation (1) with 3 and put k is 6,

$3(3x_{1} -x_{2})=3\times2\\9x_{1} -3x_{2})=6$

it means both equations are overlapped. Then, the solution has infinite solutions.

Hence, the system has an infinite solutions at k is 6 otherwise for any value of k it has no solution.