Nội dung bài giảng
Tìm x, biết:
a) \({\rm{}}{1 \over 4} + x = {{ - 1} \over 3}\)
b) \(- {3 \over 7} + x = {5 \over 8}\)
c) \(0,472 - x = 1,634\)
d) \({\rm{}} - 2,12 - x = 1{3 \over 4}\)
Giải
a) \({\rm{}}{1 \over 4} + x = {{ - 1} \over 3} \Leftrightarrow x = - {1 \over 3} - {1 \over 4}\)
\(\Leftrightarrow x = {{ - 4} \over {12}} + {{ - 3} \over {12}} \Leftrightarrow x = - {7 \over {12}}\)
b) \( - {3 \over 7} + x = {5 \over 8} \Leftrightarrow x = {5 \over 8} + {3 \over 7} \)
\(\Leftrightarrow x = {{35} \over {56}} + {{24} \over {56}} \Leftrightarrow x = {{59} \over {56}}\)
c) \(0,472 - x = 1,634 \Leftrightarrow x = 0,472 - 1,634 \)
\(\Leftrightarrow x = - 1,162\)
d) \({\rm{}} - 2,12 - x = 1{3 \over 4} \Leftrightarrow x = - 2,12 - 1{3 \over 4} \)
\(\Leftrightarrow x = - 2,12 - 1,75 \Leftrightarrow x = - 3,87\)