Friday

January 30, 2015

January 30, 2015

Posted by **Michael** on Friday, December 4, 2009 at 9:03pm.

Which of the following choices is a solution for:

(-3-i)x1 + (1-2i)x2 = 0

(-7-9i)x1 + (7-4i)x2 = 0

for any value of the variable t

[x1] = ?

[x2]

A: [5]

[1+7i] * t

B: [5]

[1-7i] * t

C: [5]

[-1-7i] * t

D: [5]

[-1+7i] * t

- Linear Algebra -
**MathMate**, Friday, December 4, 2009 at 10:00pm(-3-i)x1 + (1-2i)x2 = 0.....(1)

(-7-9i)x1 + (7-4i)x2 = 0 ....(2)

or

Ax=0

The system is a homogeneous equation. A trivial solution is x1=0 and x2=0.

For the system to have non-trivial solutions, the determinant of A must vanish, or |A|=0.

Calculate

|A|

=(-3-i)(7-4i) - (-7-9i)(1-2i)

= -21-4+5i - (-25+5i)

=0

So non-trivial solutions exist, because the two equations are linearly dependent.

Prove that the two equations are linearly dependent by applying Gauss elimination which results in two identical equations. Eliminate the second equation.

Take equation (1),

(-3-i)x1 + (1-2i)x2 = 0

We multiply by the conjugate of (1-2i) to get

(1+2i)(-3-i)x1 + (1+2i)(1-2i)x2 = 0

-(1+7i)x1 + 5x2 = 0

Let x1=5t, where t is a variable parameter, then

-(1+7i)5t + 5x2 = 0

Solving, x2=1+7i

Therefore

x1=5t, x2=1+7i

Make your pick for the answer.

- Linear Algebra -
**Michael**, Friday, December 4, 2009 at 10:39pmThanks a lot!

- Linear Algebra -
**MathMate**, Friday, December 4, 2009 at 11:42pmYou're welcome!

**Answer this Question**

**Related Questions**

college - Which of the following choices is a solution for: (-3-i)x1 + (1-2i)x2...

For Dr.Bob222 - I posted a question under First Amendment, would you look at the...

algebra 1 - sorry but on the last question i posted the wrong equation... (3x^2-...

math11 - Solve the non linear equation x^2=3x+4 graphically using a calculator, ...

math11 - Solve the non linear equation x^2=3x+4 graphically using a calculator, ...

Chemistry(I'm sooo confused here!) - The Rydberg equation, with n1=1, predicts ...

physics - please explain further - Can someone please explain the answer I got ...

math - the question is what is the solution of the equation x+2/2=4/x? 1) 1 and-...

Math - Consider the following test scores obtained by a class. Test score 90 80 ...

ALGBRA - Consider the following test scores obtained by a class. Test score 90 ...