Solve system of equations using laplace transform and evaluate x(1)

[davidbenari]

Homework Statement

I keep getting the wrong answer, and wolphram seems to back me up.

Here's the system of equations

$(-10+s)X(s)-7Y(s)=\frac{10}{s}$
$X(s)+(-2+s)Y(s)=0$

Homework Equations

The Attempt at a Solution

Using Cramer's rule I've got

$X(s)=\frac{10}{(s-9)(s-3)}-\frac{20}{s(s-9)(s-3)}$
Using partial fraction decomposition I've got

$x(t)=e^{9t}(10/6-20/54)+e^{3t}(-10/6+20/18)-20/27$

Evaluating $x(1)$ I get $10492.1$

 

[Ray Vickson]

Homework Statement

I keep getting the wrong answer, and wolphram seems to back me up.

Here's the system of equations

$(-10+s)X(s)-7Y(s)=\frac{10}{s}$
$X(s)+(-2+s)Y(s)=0$

Homework Equations

The Attempt at a Solution

Using Cramer's rule I've got

$X(s)=\frac{10}{(s-9)(s-3)}-\frac{20}{s(s-9)(s-3)}$
Using partial fraction decomposition I've got

$x(t)=e^{9t}(10/6-20/54)+e^{3t}(-10/6+20/18)-20/27$

Evaluating $x(1)$ I get $10492.1$

Your answer is correct. What makes you think it is wrong?

 

[davidbenari]

The correct answer is supposedly -1426.16 :/ Strangely enough, if I solve $y$ and evaluate $y(1)$ I get an answer close to that.

 

[Ray Vickson]

The correct answer is supposedly -1426.16 :/ Strangely enough, if I solve $y$ and evaluate $y(1)$ I get an answer close to that.

If you typed out the equations correctly, your solution is correct. So, either you mis-represented the problem, or the supposed answers are wrong.

 

[davidbenari]

Thanks for the help.