\[\eqalign{ & a]2{x \over 7} = {{ - 153} \over {63}} \cr & 2{x \over 7} = {{ - 17} \over 7} \cr & 2{x \over 7} = - 2{3 \over 7} \cr & 2{x \over 7} = 2{{ - 3} \over 7} \Leftrightarrow x = - 3 \cr & b]2{x \over 7} = {{2x + 9} \over 7} \cr & {{14 + x} \over 7} = {{2x + 9} \over 7} \cr & 14 + x = 2x + 9 \cr & 2x - x = 14 - 9 \cr & \Leftrightarrow x = 5 \cr} \]
Đề bài
Cho hỗn số \[2{x \over 7}\]. Tìm x, biết :
a] \[2{x \over 7} = {{ - 153} \over {63}}\] b] \[2{x \over 7} = {{2x + 9} \over 7}\].
Lời giải chi tiết
\[\eqalign{ & a]2{x \over 7} = {{ - 153} \over {63}} \cr & 2{x \over 7} = {{ - 17} \over 7} \cr & 2{x \over 7} = - 2{3 \over 7} \cr & 2{x \over 7} = 2{{ - 3} \over 7} \Leftrightarrow x = - 3 \cr & b]2{x \over 7} = {{2x + 9} \over 7} \cr & {{14 + x} \over 7} = {{2x + 9} \over 7} \cr & 14 + x = 2x + 9 \cr & 2x - x = 14 - 9 \cr & \Leftrightarrow x = 5 \cr} \]