by Tìm x biết: \(\frac{{14}}{{15}} – \left( {x – \frac{7}{{12}}} \right) = \frac{{31}}{{25}} – \left( {\frac{4}{{25}} – \frac{{4}}{{15}}} \right)\) Giá trị của x là:
A. \(\frac{{17}}{{10}}\)
B. \(\frac{{17}}{{100}}\)
C. \(\frac{{-7}}{{100}}\)
D. \(\frac{{-17}}{{10}}\)
Hướng dẫn
Chọn đáp án là: B
Phương pháp giải:
Thực hiện phép tính ở bên vế phải, sau đó tìm \(x – \frac{7}{{12}}\), được bao nhiêu ta cộng với \(\frac{7}{{12}}\) thì tìm ra \(x.\)
\(\begin{array}{l}\,\,\,\,\,\,\frac{{14}}{{15}} – \left( {x – \frac{7}{{12}}} \right) = \frac{{31}}{{25}} – \left( {\frac{4}{{25}} – \frac{{4}}{{15}}} \right)\\\,\,\,\,\,\,\frac{{14}}{{15}} – \left( {x – \frac{7}{{12}}} \right) = \frac{{31}}{{25}} – \frac{4}{{25}} + \frac{4}{{15}}\\\,\,\,\,\,\,\frac{{14}}{{15}} – \left( {x – \frac{7}{{12}}} \right) = \frac{{27}}{{25}} + \frac{4}{{15}}\\\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,x – \frac{7}{{12}} = \frac{{14}}{{15}} – \frac{4}{{15}} – \frac{{27}}{{25}}\\\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,x – \frac{7}{{12}}\, = \frac{2}{3} – \frac{{27}}{{25}}\\\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,x – \frac{7}{{12}} = \frac{{ – 31}}{{75}}\\\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,x\,\,\,\,\,\,\,\,\,\,\,\,\, = \frac{{ – 31}}{{75}} + \frac{7}{{12}}\\\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,x\,\,\,\,\,\,\,\,\,\,\,\,\, = \frac{{17}}{{100}}\end{array}\)
Chọn B
