Jawabanmu

2014-07-03T13:27:21+07:00
  \left[\begin{array}{ccc}-1&-2\\2&3\end{array}\right]   \left[\begin{array}{ccc}x\\y\end{array}\right] = \left[\begin{array}{ccc}-1\\9\end{array}\right]
\left[\begin{array}{ccc}-x-2y\\2x+3y\end{array}\right] = \left[\begin{array}{ccc}-1\\9\end{array}\right]

-x - 2y = -1           
   x  = 1-2y           

2x+3y = 9
[substitusi]
2(1-2y) + 3y = 9
2 - 4y + 3y = 9
   2 - y      = 9
     y    =  -7

   x  = 1-2y
   x  = 1 - 2(-7)  = 15




2014-07-03T17:05:37+07:00
-x - 2y = -1 ⇔ -2x - 4y = -2
2x+3y = 9  ⇔  2x + 3y = 9 +
                             - y = 7 atau y = -7
2x + 3y = 9 ⇒ 2x + 3(-7) = 9
                  ⇔ 2x - 21 = 9
                             2x = 9+21 = 30 ⇔ x = 30/2 = 15
Jadi, x dan y berturut-turut adalah x= 15 dan y = -7