Câu hỏi của Lê Nguyễn Minh Hằng

Question

Tìm x $\in$ Z biết:a) $\frac{1}{2}-\left(\frac{1}{3}+\frac{1}{4}\right)< x< \frac{1}{48}-\left(\frac{1}{16}-\frac{1}{6}\right)$  b) \(4\frac{5}{9}:2\frac{5}{18}-7< x< \left(3\frac{1}{5}:3,2+4,5.1\...

Kiệt ღ ๖ۣۜLý๖ۣۜ · Accepted Answer

a) $\frac{1}{2}-\left(\frac{1}{3}+\frac{1}{4}\right)< x< \frac{1}{48}-\left(\frac{1}{16}-\frac{1}{6}\right)$  Ta có: 1/2 - (1/3 + 1/4) = 1/2 - 7/12 = -1/12 ;           1/48 - (1/16 - 1/6) = 1/48 + 5/48 = 1/8Vì $-\frac{1}{12}< x< \frac{1}{8}$ nên x = 0b) $4\frac{5}{9}:2\frac{5}{18}-7< x< \left(3\frac{1}{5}:3,2+4,5.1\frac{31}{45}\right):\left(-21\frac{2}{3}\right)$Ta có :$4\frac{5}{9}:2\frac{5}{18}-7=2-7=-5$$\left(3\frac{1}{5}:3,2+4,5.1\frac{31}{45}\right):\left(-21\frac{2}{3}\right)=\left(1+\frac{38}{5}\right):\left(-21\frac{2}{3}\right)=\frac{43}{5}:\frac{-65}{3}=-\frac{129}{325}$Vì $-5< x< -\frac{129}{325}$ nên $x\in\left\{-4;-3;-2;-1\right\}$Câu trả lời: a) $\frac{1}{2}-\left(\frac{1}{3}+\frac{1}{4}\right)< x< \frac{1}{48}-\left(\frac{1}{16}-\frac{1}{6}\right)$  Ta có: 1/2 - (1/3 + 1/4) = 1/2 - 7/12 = -1/12 ;           1/48 - (1/16 - 1/6) = 1/48 + 5/48 = 1/8Vì $-\frac{1}{12}< x< \frac{1}{8}$ nên x = 0b) $4\frac{5}{9}:2\frac{5}{18}-7< x< \left(3\frac{1}{5}:3,2+4,5.1\frac{31}{45}\right):\left(-21\frac{2}{3}\right)$Ta có :$4\frac{5}{9}:2\frac{5}{18}-7=2-7=-5$$\left(3\frac{1}{5}:3,2+4,5.1\frac{31}{45}\right):\left(-21\frac{2}{3}\right)=\left(1+\frac{38}{5}\right):\left(-21\frac{2}{3}\right)=\frac{43}{5}:\frac{-65}{3}=-\frac{129}{325}$Vì $-5< x< -\frac{129}{325}$ nên $x\in\left\{-4;-3;-2;-1\right\}$

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