Tìm chỗ sai trong mỗi lời giải sau và giải lại cho đúng:a) begin{array}{l}5 - left( {x + 8} right) 3x + 3left( {x - 9} right),,,,5 - x + 8 3x + 3x - 27,,,,,,,,,13 - x 6x - 27,,,,, - x - 6x - 27 + 13,,,,,,,,,,,,, - 7x - 14,,,,,,,,,,,,,,,,,,,x left( { - 14} right):left( { - 7} right),,,,,,,,,,,,,,,,,,,x 2.end{array}Vậy phương trình có nghiệm x 2.b) begin{array}{l}3x - 18 + x 12 - left( {5x + 3} right),,,,,,,4x - 18 12 - 5x - 3,,,,,,,4x + 5x 9 - 18,,,,,,,,,,,,,,,,,9x - 9,,,,,,,...
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Tìm chỗ sai trong mỗi lời giải sau và giải lại cho đúng:
a)
\(\begin{array}{l}5 - \left( {x + 8} \right) = 3x + 3\left( {x - 9} \right)\\\,\,\,\,5 - x + 8 = 3x + 3x - 27\\\,\,\,\,\,\,\,\,\,13 - x = 6x - 27\\\,\,\,\,\, - x - 6x = - 27 + 13\\\,\,\,\,\,\,\,\,\,\,\,\,\, - 7x = - 14\\\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,x = \left( { - 14} \right):\left( { - 7} \right)\\\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,x = 2.\end{array}\)
Vậy phương trình có nghiệm \(x = 2\).
b)
\(\begin{array}{l}3x - 18 + x = 12 - \left( {5x + 3} \right)\\\,\,\,\,\,\,\,4x - 18 = 12 - 5x - 3\\\,\,\,\,\,\,\,4x + 5x = 9 - 18\\\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,9x = - 9\\\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,x = \left( { - 9} \right):9\\\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,x = - 1.\end{array}\)
Vậy phương trình có nghiệm \(x = - 1\).
