Definition of linearly independent

In summary, linearly independent equations are those that are linear and cannot be derived from one another through algebraic manipulation. A system with linearly independent equations will always have a unique solution, but the reverse is not always true.
  • #1
Zoe-b
98
0
I've looked it up and can't really find a clear answer..
For a system of 3 simultaneous linear equations, is there any difference between 'the equations are linearly independent' and 'the equations have a unique solution'. If so what is it?
Thanks!
 
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  • #2
Two or more equations are linearly independent if they are:

a) linear (ie, no terms with power > 1 and no multiplication of variables by each other),
b) independent (none of the equations can be derived algebraically from the others).

Some examples:

Linearly independent:
2x + 3y = 8
3x + 2y = 5

x + y + z = 7
3x + 2y = 17

Not linearly independent:
x + y = 4
2x + 2y = 8
(second equation is a multiple of the first)

x+y=3
x+2y=9
2x+3y=12
(third equation is sum of the first two)

x2 + y = 1
x + 3y = 9
(equation is quadratic, not linear)

xy + 3y = 6
(xy term makes equation not linear)

A system of linearly independent equations need not be consistent, but if the left-hand sides of all the equations are linearly independent, then it always will be.
 
  • #3
Hmmn.. thanks that does help.
I guess what I really meant is if a system of equations has a unique solution then is it always linearly independent?
 
  • #5
hgfalling said:
Two or more equations are linearly independent if they are:

a) linear (ie, no terms with power > 1 and no multiplication of variables by each other),
b) independent (none of the equations can be derived algebraically from the others).
Condition (a) is not required. For example, the functions f(x)=x and g(x)=x2 are linearly independent.

Condition (b) is not quite correct. Better said, a set of expressions {f1(x1,x2,...), f2(x1,x2,...), ...} are linearly independent if the only solution to a1f1+a2f2+...=0 is the trivial solution a1=a2=...=0.
 

Related to Definition of linearly independent

1. What does it mean for a set of vectors to be linearly independent?

Linear independence refers to a set of vectors in a vector space that cannot be written as a linear combination of other vectors in the same space. In other words, none of the vectors in the set can be expressed as a combination of the others, making them all necessary for the span of the vector space.

2. How do you test for linear independence?

To test for linear independence, you can use the determinant method or the rank method. The determinant method involves creating a matrix with the vectors as columns and calculating the determinant. If the determinant is non-zero, the vectors are linearly independent. The rank method involves creating a matrix with the vectors as rows and reducing it to row-echelon form. If all the rows are pivot rows, the vectors are linearly independent.

3. What are some examples of linearly independent vectors?

One example of linearly independent vectors is the standard basis vectors in a 3-dimensional space: (1, 0, 0), (0, 1, 0), and (0, 0, 1). Another example is the vectors (1, 2) and (3, 4) in a 2-dimensional space.

4. Can a set of linearly dependent vectors be linearly independent?

No, a set of linearly dependent vectors cannot be linearly independent. If a set of vectors is linearly dependent, it means that at least one vector can be written as a linear combination of the others, making it unnecessary for the span of the vector space. Therefore, the set cannot be linearly independent.

5. How is linear independence related to vector spaces?

Linear independence is a fundamental concept in vector spaces. It allows us to determine if a set of vectors forms a basis for the vector space, which is a set of linearly independent vectors that can span the entire space. In other words, linear independence is a crucial property for creating a basis for a vector space.

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