Linear Algebra Examples
[-12-66][−12−66]
Step 1
Step 1.1
Set up the formula to find the characteristic equation p(λ)p(λ).
p(λ)=determinant(A-λI2)p(λ)=determinant(A−λI2)
Step 1.2
The identity matrix or unit matrix of size 22 is the 2×22×2 square matrix with ones on the main diagonal and zeros elsewhere.
[1001][1001]
Step 1.3
Substitute the known values into p(λ)=determinant(A-λI2)p(λ)=determinant(A−λI2).
Step 1.3.1
Substitute [-12-66][−12−66] for AA.
p(λ)=determinant([-12-66]-λI2)p(λ)=determinant([−12−66]−λI2)
Step 1.3.2
Substitute [1001][1001] for I2I2.
p(λ)=determinant([-12-66]-λ[1001])p(λ)=determinant([−12−66]−λ[1001])
p(λ)=determinant([-12-66]-λ[1001])p(λ)=determinant([−12−66]−λ[1001])
Step 1.4
Simplify.
Step 1.4.1
Simplify each term.
Step 1.4.1.1
Multiply -λ−λ by each element of the matrix.
p(λ)=determinant([-12-66]+[-λ⋅1-λ⋅0-λ⋅0-λ⋅1])p(λ)=determinant([−12−66]+[−λ⋅1−λ⋅0−λ⋅0−λ⋅1])
Step 1.4.1.2
Simplify each element in the matrix.
Step 1.4.1.2.1
Multiply -1−1 by 11.
p(λ)=determinant([-12-66]+[-λ-λ⋅0-λ⋅0-λ⋅1])p(λ)=determinant([−12−66]+[−λ−λ⋅0−λ⋅0−λ⋅1])
Step 1.4.1.2.2
Multiply -λ⋅0−λ⋅0.
Step 1.4.1.2.2.1
Multiply 00 by -1−1.
p(λ)=determinant([-12-66]+[-λ0λ-λ⋅0-λ⋅1])p(λ)=determinant([−12−66]+[−λ0λ−λ⋅0−λ⋅1])
Step 1.4.1.2.2.2
Multiply 00 by λλ.
p(λ)=determinant([-12-66]+[-λ0-λ⋅0-λ⋅1])p(λ)=determinant([−12−66]+[−λ0−λ⋅0−λ⋅1])
p(λ)=determinant([-12-66]+[-λ0-λ⋅0-λ⋅1])p(λ)=determinant([−12−66]+[−λ0−λ⋅0−λ⋅1])
Step 1.4.1.2.3
Multiply -λ⋅0−λ⋅0.
Step 1.4.1.2.3.1
Multiply 00 by -1−1.
p(λ)=determinant([-12-66]+[-λ00λ-λ⋅1])p(λ)=determinant([−12−66]+[−λ00λ−λ⋅1])
Step 1.4.1.2.3.2
Multiply 00 by λλ.
p(λ)=determinant([-12-66]+[-λ00-λ⋅1])p(λ)=determinant([−12−66]+[−λ00−λ⋅1])
p(λ)=determinant([-12-66]+[-λ00-λ⋅1])p(λ)=determinant([−12−66]+[−λ00−λ⋅1])
Step 1.4.1.2.4
Multiply -1−1 by 11.
p(λ)=determinant([-12-66]+[-λ00-λ])p(λ)=determinant([−12−66]+[−λ00−λ])
p(λ)=determinant([-12-66]+[-λ00-λ])p(λ)=determinant([−12−66]+[−λ00−λ])
p(λ)=determinant([-12-66]+[-λ00-λ])p(λ)=determinant([−12−66]+[−λ00−λ])
Step 1.4.2
Add the corresponding elements.
p(λ)=determinant[-1-λ2+0-6+06-λ]
Step 1.4.3
Simplify each element.
Step 1.4.3.1
Add 2 and 0.
p(λ)=determinant[-1-λ2-6+06-λ]
Step 1.4.3.2
Add -6 and 0.
p(λ)=determinant[-1-λ2-66-λ]
p(λ)=determinant[-1-λ2-66-λ]
p(λ)=determinant[-1-λ2-66-λ]
Step 1.5
Find the determinant.
Step 1.5.1
The determinant of a 2×2 matrix can be found using the formula |abcd|=ad-cb.
p(λ)=(-1-λ)(6-λ)-(-6⋅2)
Step 1.5.2
Simplify the determinant.
Step 1.5.2.1
Simplify each term.
Step 1.5.2.1.1
Expand (-1-λ)(6-λ) using the FOIL Method.
Step 1.5.2.1.1.1
Apply the distributive property.
p(λ)=-1(6-λ)-λ(6-λ)-(-6⋅2)
Step 1.5.2.1.1.2
Apply the distributive property.
p(λ)=-1⋅6-1(-λ)-λ(6-λ)-(-6⋅2)
Step 1.5.2.1.1.3
Apply the distributive property.
p(λ)=-1⋅6-1(-λ)-λ⋅6-λ(-λ)-(-6⋅2)
p(λ)=-1⋅6-1(-λ)-λ⋅6-λ(-λ)-(-6⋅2)
Step 1.5.2.1.2
Simplify and combine like terms.
Step 1.5.2.1.2.1
Simplify each term.
Step 1.5.2.1.2.1.1
Multiply -1 by 6.
p(λ)=-6-1(-λ)-λ⋅6-λ(-λ)-(-6⋅2)
Step 1.5.2.1.2.1.2
Multiply -1(-λ).
Step 1.5.2.1.2.1.2.1
Multiply -1 by -1.
p(λ)=-6+1λ-λ⋅6-λ(-λ)-(-6⋅2)
Step 1.5.2.1.2.1.2.2
Multiply λ by 1.
p(λ)=-6+λ-λ⋅6-λ(-λ)-(-6⋅2)
p(λ)=-6+λ-λ⋅6-λ(-λ)-(-6⋅2)
Step 1.5.2.1.2.1.3
Multiply 6 by -1.
p(λ)=-6+λ-6λ-λ(-λ)-(-6⋅2)
Step 1.5.2.1.2.1.4
Rewrite using the commutative property of multiplication.
p(λ)=-6+λ-6λ-1⋅-1λ⋅λ-(-6⋅2)
Step 1.5.2.1.2.1.5
Multiply λ by λ by adding the exponents.
Step 1.5.2.1.2.1.5.1
Move λ.
p(λ)=-6+λ-6λ-1⋅-1(λ⋅λ)-(-6⋅2)
Step 1.5.2.1.2.1.5.2
Multiply λ by λ.
p(λ)=-6+λ-6λ-1⋅-1λ2-(-6⋅2)
p(λ)=-6+λ-6λ-1⋅-1λ2-(-6⋅2)
Step 1.5.2.1.2.1.6
Multiply -1 by -1.
p(λ)=-6+λ-6λ+1λ2-(-6⋅2)
Step 1.5.2.1.2.1.7
Multiply λ2 by 1.
p(λ)=-6+λ-6λ+λ2-(-6⋅2)
p(λ)=-6+λ-6λ+λ2-(-6⋅2)
Step 1.5.2.1.2.2
Subtract 6λ from λ.
p(λ)=-6-5λ+λ2-(-6⋅2)
p(λ)=-6-5λ+λ2-(-6⋅2)
Step 1.5.2.1.3
Multiply -(-6⋅2).
Step 1.5.2.1.3.1
Multiply -6 by 2.
p(λ)=-6-5λ+λ2--12
Step 1.5.2.1.3.2
Multiply -1 by -12.
p(λ)=-6-5λ+λ2+12
p(λ)=-6-5λ+λ2+12
p(λ)=-6-5λ+λ2+12
Step 1.5.2.2
Add -6 and 12.
p(λ)=-5λ+λ2+6
Step 1.5.2.3
Reorder -5λ and λ2.
p(λ)=λ2-5λ+6
p(λ)=λ2-5λ+6
p(λ)=λ2-5λ+6
Step 1.6
Set the characteristic polynomial equal to 0 to find the eigenvalues λ.
λ2-5λ+6=0
Step 1.7
Solve for λ.
Step 1.7.1
Factor λ2-5λ+6 using the AC method.
Step 1.7.1.1
Consider the form x2+bx+c. Find a pair of integers whose product is c and whose sum is b. In this case, whose product is 6 and whose sum is -5.
-3,-2
Step 1.7.1.2
Write the factored form using these integers.
(λ-3)(λ-2)=0
(λ-3)(λ-2)=0
Step 1.7.2
If any individual factor on the left side of the equation is equal to 0, the entire expression will be equal to 0.
λ-3=0
λ-2=0
Step 1.7.3
Set λ-3 equal to 0 and solve for λ.
Step 1.7.3.1
Set λ-3 equal to 0.
λ-3=0
Step 1.7.3.2
Add 3 to both sides of the equation.
λ=3
λ=3
Step 1.7.4
Set λ-2 equal to 0 and solve for λ.
Step 1.7.4.1
Set λ-2 equal to 0.
λ-2=0
Step 1.7.4.2
Add 2 to both sides of the equation.
λ=2
λ=2
Step 1.7.5
The final solution is all the values that make (λ-3)(λ-2)=0 true.
λ=3,2
λ=3,2
λ=3,2
Step 2
The eigenvector is equal to the null space of the matrix minus the eigenvalue times the identity matrix where N is the null space and I is the identity matrix.
εA=N(A-λI2)
Step 3
Step 3.1
Substitute the known values into the formula.
N([-12-66]-3[1001])
Step 3.2
Simplify.
Step 3.2.1
Simplify each term.
Step 3.2.1.1
Multiply -3 by each element of the matrix.
[-12-66]+[-3⋅1-3⋅0-3⋅0-3⋅1]
Step 3.2.1.2
Simplify each element in the matrix.
Step 3.2.1.2.1
Multiply -3 by 1.
[-12-66]+[-3-3⋅0-3⋅0-3⋅1]
Step 3.2.1.2.2
Multiply -3 by 0.
[-12-66]+[-30-3⋅0-3⋅1]
Step 3.2.1.2.3
Multiply -3 by 0.
[-12-66]+[-300-3⋅1]
Step 3.2.1.2.4
Multiply -3 by 1.
[-12-66]+[-300-3]
[-12-66]+[-300-3]
[-12-66]+[-300-3]
Step 3.2.2
Add the corresponding elements.
[-1-32+0-6+06-3]
Step 3.2.3
Simplify each element.
Step 3.2.3.1
Subtract 3 from -1.
[-42+0-6+06-3]
Step 3.2.3.2
Add 2 and 0.
[-42-6+06-3]
Step 3.2.3.3
Add -6 and 0.
[-42-66-3]
Step 3.2.3.4
Subtract 3 from 6.
[-42-63]
[-42-63]
[-42-63]
Step 3.3
Find the null space when λ=3.
Step 3.3.1
Write as an augmented matrix for Ax=0.
[-420-630]
Step 3.3.2
Find the reduced row echelon form.
Step 3.3.2.1
Multiply each element of R1 by -14 to make the entry at 1,1 a 1.
Step 3.3.2.1.1
Multiply each element of R1 by -14 to make the entry at 1,1 a 1.
[-14⋅-4-14⋅2-14⋅0-630]
Step 3.3.2.1.2
Simplify R1.
[1-120-630]
[1-120-630]
Step 3.3.2.2
Perform the row operation R2=R2+6R1 to make the entry at 2,1 a 0.
Step 3.3.2.2.1
Perform the row operation R2=R2+6R1 to make the entry at 2,1 a 0.
[1-120-6+6⋅13+6(-12)0+6⋅0]
Step 3.3.2.2.2
Simplify R2.
[1-120000]
[1-120000]
[1-120000]
Step 3.3.3
Use the result matrix to declare the final solution to the system of equations.
x-12y=0
0=0
Step 3.3.4
Write a solution vector by solving in terms of the free variables in each row.
[xy]=[y2y]
Step 3.3.5
Write the solution as a linear combination of vectors.
[xy]=y[121]
Step 3.3.6
Write as a solution set.
{y[121]|y∈R}
Step 3.3.7
The solution is the set of vectors created from the free variables of the system.
{[121]}
{[121]}
{[121]}
Step 4
Step 4.1
Substitute the known values into the formula.
N([-12-66]-2[1001])
Step 4.2
Simplify.
Step 4.2.1
Simplify each term.
Step 4.2.1.1
Multiply -2 by each element of the matrix.
[-12-66]+[-2⋅1-2⋅0-2⋅0-2⋅1]
Step 4.2.1.2
Simplify each element in the matrix.
Step 4.2.1.2.1
Multiply -2 by 1.
[-12-66]+[-2-2⋅0-2⋅0-2⋅1]
Step 4.2.1.2.2
Multiply -2 by 0.
[-12-66]+[-20-2⋅0-2⋅1]
Step 4.2.1.2.3
Multiply -2 by 0.
[-12-66]+[-200-2⋅1]
Step 4.2.1.2.4
Multiply -2 by 1.
[-12-66]+[-200-2]
[-12-66]+[-200-2]
[-12-66]+[-200-2]
Step 4.2.2
Add the corresponding elements.
[-1-22+0-6+06-2]
Step 4.2.3
Simplify each element.
Step 4.2.3.1
Subtract 2 from -1.
[-32+0-6+06-2]
Step 4.2.3.2
Add 2 and 0.
[-32-6+06-2]
Step 4.2.3.3
Add -6 and 0.
[-32-66-2]
Step 4.2.3.4
Subtract 2 from 6.
[-32-64]
[-32-64]
[-32-64]
Step 4.3
Find the null space when λ=2.
Step 4.3.1
Write as an augmented matrix for Ax=0.
[-320-640]
Step 4.3.2
Find the reduced row echelon form.
Step 4.3.2.1
Multiply each element of R1 by -13 to make the entry at 1,1 a 1.
Step 4.3.2.1.1
Multiply each element of R1 by -13 to make the entry at 1,1 a 1.
[-13⋅-3-13⋅2-13⋅0-640]
Step 4.3.2.1.2
Simplify R1.
[1-230-640]
[1-230-640]
Step 4.3.2.2
Perform the row operation R2=R2+6R1 to make the entry at 2,1 a 0.
Step 4.3.2.2.1
Perform the row operation R2=R2+6R1 to make the entry at 2,1 a 0.
[1-230-6+6⋅14+6(-23)0+6⋅0]
Step 4.3.2.2.2
Simplify R2.
[1-230000]
[1-230000]
[1-230000]
Step 4.3.3
Use the result matrix to declare the final solution to the system of equations.
x-23y=0
0=0
Step 4.3.4
Write a solution vector by solving in terms of the free variables in each row.
[xy]=[2y3y]
Step 4.3.5
Write the solution as a linear combination of vectors.
[xy]=y[231]
Step 4.3.6
Write as a solution set.
{y[231]|y∈R}
Step 4.3.7
The solution is the set of vectors created from the free variables of the system.
{[231]}
{[231]}
{[231]}
Step 5
The eigenspace of A is the list of the vector space for each eigenvalue.
{[121],[231]}