1. Thực hiện phép tính (tính nhanh nếu có thể): a) 9/4:- 3/10; 2. Tìm \[x\]: a) - 1/2:x = 1/3;
Giải thích
1.
a) \[\frac{9}{4}:\frac{{ - 3}}{{10}}\] \[ = \frac{9}{4}.\frac{{10}}{{ - 3}}\] \[ = \frac{{9.10}}{{4.\left( { - 3} \right)}}\]\( = \frac{{15}}{{ - 2}}\) \( = \frac{{ - 15}}{2}\);
b) \[\frac{{ - 5}}{3}.\frac{{11}}{{25}} + \frac{{ - 5}}{3}.\frac{{14}}{{25}}\]\[ = \frac{{ - 5}}{3}\left( {\frac{{11}}{{25}} + \frac{{14}}{{25}}} \right)\]\[ = \frac{{ - 5}}{3}.\frac{{25}}{{25}} = \frac{{ - 5}}{3}\].
2.
a) \[\frac{{ - 1}}{2}:x = \frac{1}{3}\] \[x = \frac{{ - 1}}{2}:\frac{1}{3}\] \[x = \frac{{ - 1}}{2}.3\] \[x = \frac{{ - 3}}{2}\] Vậy \[x = \frac{{ - 3}}{2}\] | b) \[\frac{2}{3}x + \frac{1}{2} = \frac{3}{4}\] \[\frac{2}{3}x = \frac{3}{4} - \frac{1}{2}\] \[\frac{2}{3}x = \frac{1}{4}\] \[x = \frac{1}{4}:\frac{2}{3}\] \[x = \frac{3}{8}\] Vậy \[x = \frac{3}{8}\]. |