Bài 153 trang 40 SBT toán 6 tập 2

Tìm \(\displaystyle x\) biết:\(\displaystyle \left( {{1 \over {12}} + 3{1 \over 6} - 30,75} \right).x - 8 \)\(\displaystyle= \left( {{3 \over 5} + 0,415 + {1 \over {200}}} \right):0,01\)

Lời giải

\(\displaystyle \left( {{1 \over {12}} + 3{1 \over 6} - 30,75} \right).x - 8 \)\(\displaystyle= \left( {{3 \over 5} + 0,415 + {1 \over {200}}} \right):0,01\)

\(\displaystyle  \Rightarrow \left( {{1 \over {12}} + {{19} \over 6} - 30{1 \over 4}} \right).x - 8 \)\(\displaystyle= \left( {0,6 + 0,415 + 0,005} \right):0,01 \)
\(\displaystyle \Rightarrow \left( {{1 \over {12}} + {{38} \over {12}} - {{369} \over {12}}} \right).x - 8 \)\(\displaystyle = 1,02:0,01 \) 

\(\displaystyle \eqalign{
& \Rightarrow {{ - 55} \over 2}x - 8 =102\cr 
& \Rightarrow {{ - 55} \over 2}x = 102 + 8 \cr 
& \Rightarrow {{ - 55} \over 2}x = 110 \cr 
& \Rightarrow x = 110:{{ - 55} \over 2} \cr&\Rightarrow x= 110.{{ - 2} \over {55}} = - 4 \cr} \)


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