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jawab
12
cara invers :

[tex] \left[\begin{array}{ccc}x\\y\end{array}\right]\,=\, \frac{1}{18+20} \left[\begin{array}{ccc}-6&4\\-5&3\end{array}\right] \left[\begin{array}{ccc}2\\4\end{array}\right]\,=\, \left[\begin{array}{ccc}2\\1\end{array}\right] [/tex]

cara determinan

[tex]det\,D\,= \left|\begin{array}{ccc}3&-4\\5&-6\end{array}\right] \,=\,3(-6)-5(-4)=2[/tex]

[tex]det\,X\,= \left|\begin{array}{ccc}2&-4\\4&-6\end{array}\right] \,=\,2(-6)-4(-4)=4[/tex]

[tex]det\,Y\,= \left|\begin{array}{ccc}3&2\\5&4\end{array}\right] \,=\,3(4)- 5(2)= 2[/tex]

x = Dx/D = 4/2 = 2
y = Dy/D = 2/2 = 1

11. 
det A =  3 (2)  2(-4) = 14
det B = -1(2) -4(5) = -22
det A. det B = 14 (-22) = - 308

[tex] A\,B\,= \left[\begin{array}{ccc}-9&7\\6&14\end{array}\right]\,; det\,A\,.B\,=-9(14)-6(7) = - 308[/tex]

det A. det B = det(A.B)

10)
x + y = 4x - 5y 
-3x  = - 6y
x = 2y

2x - 15 = 6x + 7y
-4x - 7y = 15
-4(2y) - 7y = 15
-15y = 15
y = -1
x= 2y
x = -2
(x,y)= (- 2, - 1)

9)

[tex] \left[\begin{array}{ccc}8&3&5\end{array}\right] \left[\begin{array}{ccc}200\\2000\\1500\end{array}\right] \,=\, \left[8(200)+3(2000)+5(1500}\right]\,=15.100 [/tex]

1)
a)  x ≥  20
b)  0 ≤ x ≤ 32
c) 5 ≤ x ≤ 10

3)
-3x + 2y ≥ 6
x = 0 , y = 3
y = 0 , x = -2
DHP (gambar no .3)

4) 
3x - 5y ≤ 15
x = 0, y = - 3
y = 0, x = 5
5 < y < 10
5 < x< 10
DHP (gambar no. 4)