How do solve the following linear system?: 1/3x + 3y = 9 , 8x + 3y= -9 13x+3y=9,8x+3y=9?

1 Answer
Dec 26, 2015

You can solve it either using substitution or elimination, but the following proof will use substitution.

Explanation:

1/3x13x + 3y = 9
3y = 9 - 1/3x13x
y = 3 - 1/9x19x
8x + 3(3 - 1/9x19x) = -9
8x + 9 - 1/3x13x = -9
23/3x233x + 9 = -9
23/3x233x = -18
23 = -54x
-54/235423 = x
8(-54/235423) + 3y = -9
-432/2343223 + 3y = -9
-432/2343223 + 9 = -3y
-225/2322523 = -3y
75/237523 = y

The solution set is (-54/235423, 75/237523)