Tìm x biết:
\(\left( {{1 \over {12}} + 3{1 \over 6} – 30,75} \right).x – 8 = \left( {{3 \over 5} + 0,415 + {1 \over {200}}} \right):0,01\)
Giải
\(\left( {{1 \over {12}} + 3{1 \over 6} – 30,75} \right).x – 8 = \left( {{3 \over 5} + 0,415 + {1 \over {200}}} \right):0,01\)
\(\eqalign{
& \Leftrightarrow \left( {{1 \over {12}} + {{19} \over 6} – 30{1 \over 4}} \right).x – 8 = \left( {0,6 + 0,415 + 0,005} \right):0,01 \cr
& \Leftrightarrow \left( {{1 \over {12}} + {{38} \over {12}} – {{369} \over {12}}} \right).x – 8 = 1,02:0,01 \cr} \)
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\(\eqalign{
& \Leftrightarrow {{ – 55} \over 2}x – 8 = {{102} \over {100}}.{{100} \over 1} \cr
& \Leftrightarrow {{ – 55} \over 2}x = 102 + 8 \cr
& \Leftrightarrow {{ – 55} \over 2}x = 110 \cr
& \Leftrightarrow x = 110:{{ – 55} \over 2} = 110.{{ – 2} \over {55}} = – 4 \cr} \)