I need help solving two linear equations using Gaussian Elimination. The equations are: x-3y=1 and 2x+5y=9

Question

I need help solving two linear equations using Gaussian Elimination.  The equations are:  x-3y=1 and 2x+5y=9

anonymous · Answer

multiply first equation by -2 and add to second to get 
\][11y=7\] or 
$$y=\frac{7}{11}$$

anonymous · Answer

that is 
$$-2x+6y=-2$$
+$$2x+5y=9$$
$$11y=7$$
$$y=\frac{7}{11}$$

anonymous · Answer

The book says the answers are 2,1.  I multiplied 7/11 by 11/7 to get the one.  Is this correct?

anonymous · Answer

book says answers are x = 2 and y = 1?

anonymous · Answer

yup

anonymous · Answer

well then i think there is a typo on your first equation

anonymous · Answer

I got 2 by plugging in the one for y into the 2x+5=9 equation

anonymous · Answer

should be x - 3y = -1 yes?

anonymous · Answer

x-3y=-1 it should be!

anonymous · Answer

otherwise (2,1) is wrong for sure, since 2 - 3  is not 1

anonymous · Answer

right!

anonymous · Answer

Thanks!

anonymous · Answer

want to do another one?

anonymous · Answer

ok so lets start again with the correct equations 
$$x-3y=-1$$
$$2x+5y=9$$

anonymous · Answer

multiply the first by -2 to get 
$$-2x+6y=2$$
$$2x+5y=9$$ add to get 
$$11y=11$$ so 
$$y=1$$

anonymous · Answer

Amazing how one little sign can throw it all off.