Question

Explain, in complete sentences, how you would use the elimination method to solve the following system of equations. Provide the solution to the system.

6x – 5y = 4
9x + 4y = –17

Answer 1

write it in matrix form (I'm not an artist so I'll just write it this way):

6,-5,4
9,4,-17

write that matrix in reduced row echelon form:

1,0,-1
0,1,-2

x = -1, y = -2

Answer 2

6x – 5y = 4
9x + 4y = –17
-------------
4*(6x – 5y = 4)
5*(9x + 4y = –17)
----------------
24x – 20y = 16
45x + 20y = –85
--------------(add the above 2 eqns)
69x=-69
x=-1
plug x=-1 in 6x – 5y = 4
6*(-1)-5y=4
-6-5y=4
-5y=10
y=-2

so x=-1 and y=-2