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Giải các phương trình sau:
a. \(3x + 1 = 7x – 11\)
b. \(5 – 3x = 6x + 7\)
c. \(11 – 2x = x – 1\)
d. \(15 – 8x = 9 – 5x\)
a. \(3x + 1 = 7x – 11\)
\(\eqalign{ & \Leftrightarrow 3x – 7x = – 11 – 1 \cr & \Leftrightarrow – 4x = – 12 \Leftrightarrow x = 3 \cr} \)
b. \(5 – 3x = 6x + 7\)
\(\eqalign{ & \Leftrightarrow 5 – 7 = 6x + 3x \cr & \Leftrightarrow – 2 = 9x \Leftrightarrow x = – {2 \over 9} \cr} \)
c. \(11 – 2x = x – 1\)
\(\eqalign{ & \Leftrightarrow 11 + 1 = x + 2x \cr & \Leftrightarrow 12 = 3x \Leftrightarrow x = 4 \cr} \)
d. \(15 – 8x = 9 – 5x\)
\(\eqalign{ & \Leftrightarrow – 8x + 5x = 9 – 15 \cr & \Leftrightarrow – 3x = – 6 \Leftrightarrow x = 2 \cr} \)