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jawab
1)
(a₂₃)² - a₁₄ + a₄₂= 
= (-2)² - (7) + (1)
= 4 - 6
= - 2

2)  A + 2B = C
2x  - 1 + 2(3) = 1
2x - 1 +6 = 1
2x + 5 = 1
2x = - 4
x = - 2

x+ y + 2x = 3
3x + y = 3 
3(-2) + y = 3
y = 9

2y - x = 2(9) - (-2)
2y - x = 20


3) B. A=  C

[tex] \left[\begin{array}{ccc}1&-1&0\\0&2&3\end{array}\right] \left[\begin{array}{ccc}2&1\\3&1\\1&-2\end{array}\right] \,= \left[\begin{array}{ccc}-1&-2\\9&-4\end{array}\right] [/tex]

[tex]C\,= \left[\begin{array}{ccc}-1&-2\\9&4\end{array}\right][/tex]


[tex]C^{T}\,= \left[\begin{array}{ccc}-1&9\\-2&-4\end{array}\right][/tex]