Toán Lớp 10: +1a+3b-3c=-8
+2a-2b-5c=+23
-5a-1b-1c=-14
Giúp vs ạ
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Toán Lớp 10: +1a+3b-3c=-8
+2a-2b-5c=+23
-5a-1b-1c=-14
Giúp vs ạ
Comments ( 2 )
\quad \begin{cases}a + 3b – 3c = -8\qquad\ (1)\\2a – 2b – 5c = 23\qquad (2)\\-5a – b – c = -14\quad\ \ (3)\end{cases}\\
(1)(2) \Leftrightarrow \begin{cases}2a + 6b – 6c = -16\\2a – 2b – 5c = 23\end{cases}\Leftrightarrow 8b – c = -39\qquad\qquad\ \ (4)\\
(1)(3)\Leftrightarrow \begin{cases}5a + 15b – 15c = -40\\-5a – b – c = -14\end{cases}\Leftrightarrow 14b – 16c = -54\qquad (5)\\
(4)(5)\Leftrightarrow \begin{cases}8b – c = -39\\7b – 8c = -27\end{cases} \Leftrightarrow \begin{cases}b = -5\\c = -1\end{cases}\\
\text{Thay vào $(1)$ ta được:}\\
\quad a + 3.(-5) – 3.(-1) = -8\Leftrightarrow a = 4\\
\text{Vậy}\ (a;b;c)=(4;-5;-1)
\end{array}\)