I am having difficulty with true/false statements and their justifications regarding systems of line

mllewestblam2

mllewestblam2

Answered question

2022-06-03

I am having difficulty with true/false statements and their justifications regarding systems of linear equations.
(a) A linear system of three equations in five unknowns is always consistent (i.e. it has at least one solution)
(b) A linear system of five equations in three unknowns cannot be consistent
(c) If a linear system in echelon form is triangular then the system has the unique solution
(d) If a linear system of n equations in n unknowns has two equations that are multiples of one another, then the system is inconsistent.
So far, for (a) I have said False, as it will always be consistent if it is homogeneous, but not if it is non-homogeneous.
For (b) I have said false, but am having difficulty justifying this assertion
c) I know to be true.
(d) I believe may be false as having equations that are multiples could result in free variables and hence infinite solutions?
I am rather unsure on what I have done so far.
Any assistance is greatly appreciated.

Answer & Explanation

zuiverevv03m

zuiverevv03m

Beginner2022-06-04Added 1 answers

for part b , you may consider below counter example:
x 1 + x 2 + x 3 = 1
for part d:
you're correct about the answer but your reasoning is only partially correct - the system can also be inconsistent:
x 1 + x 2 + x 3 = 1
2 x 1 + 2 x 2 + 2 x 3 = 2
x 1 + x 2 + x 3 = 2
Jabari Pitts

Jabari Pitts

Beginner2022-06-05Added 2 answers

for part(1), I can give one example a+b+c+d+e=1,2a+b+c+d+e=2,3a+b+c+d+e=5, this system of three equations in 5 variables has no solution or it is inconsistent.Hence the given statement is false. for part(2), we can have one example a+b+c=3, 2a+2b+c=5, 2a+b+2c=5, a+2b+2c=5, a+b+2c=4. This is a system of five equations in 3 variables with solution a=b=c=1. Hence the given statement is false.

Do you have a similar question?

Recalculate according to your conditions!

Ask your question.
Get an expert answer.

Let our experts help you. Answer in as fast as 15 minutes.

Didn't find what you were looking for?