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\(a)\frac{x}{8}=\frac{-30}{y}=\frac{-48}{32}\)
Rút gọn : \(\frac{-48}{32}=\frac{(-48):16}{32:16}=\frac{-3}{2}\)
* Ta có : \(\frac{x}{8}=\frac{-3}{2}\)
\(\Rightarrow x\cdot2=-3\cdot8\)
\(\Rightarrow x=\frac{-3\cdot8}{2}=-12\)
* Ta có : \(\frac{-30}{y}=\frac{-3}{2}\)
\(\Rightarrow-30\cdot2=-3\cdot y\)
\(\Rightarrow y=\frac{-30\cdot2}{-3}=20\)
Mấy bài kia làm tương tự
\(\left(3x-1\right)⋮\left(x+1\right)\)
\(\Rightarrow\left(3x+3-4\right)⋮\left(x+1\right)\)
\(\Rightarrow\left(-4\right)⋮\left(x+1\right)\)
\(\Rightarrow x+1\inƯ\left(-4\right)=\left\{-4;-1;1;4\right\}\)
\(\Rightarrow x\in\left\{-5;-2;0;3\right\}\)
a) Ta có : \(0< \left|x+1\right|\le3\)
\(\Rightarrow\left|x+1\right|\in\left\{1;2;3\right\}\)
\(\Rightarrow x+1\in\left\{-1;1;-2;2;-3;3\right\}\)
\(\Rightarrow x\in\left\{-2;0;-3;1;-4;2\right\}\)
b) Ta có : \(0< \left|x\right|< 3\)
\(\Rightarrow\left|x\right|\in\left\{1;2\right\}\)
\(\Rightarrow x\in\left\{\pm1;\pm2\right\}\)
c) Ta có : \(-3\le\left|x+1\right|\le3\)
\(\Rightarrow\left|x+1\right|\in\left\{0;1;2;3\right\}\)
\(\Rightarrow x+1\in\left\{0;-1;1;-2;2;-3;3\right\}\)
\(\Rightarrow x\in\left\{-1;-2;0;-3;1;-4;2\right\}\)
\(a,\frac{3}{4}.\left(x+2\right)+\frac{1}{2}.\left(x-\frac{1}{2}\right)=\frac{15}{4}\)
\(\frac{3}{4}.x+\frac{3}{4}.2+\frac{1}{2}.x+\frac{1}{2}.\left(-\frac{1}{2}\right)=\frac{15}{4}\)
\(\left(\frac{3}{4}.x+\frac{1}{2}.x\right)+\frac{3}{2}-\frac{1}{4}=\frac{15}{4}\)
\(\left(\frac{3}{4}+\frac{1}{3}\right).x=\frac{15}{4}+\frac{1}{4}-\frac{3}{2}\)
\(\frac{5}{4}.x=\frac{5}{2}\)
\(x=\frac{5}{2}:\frac{5}{4}\)
\(x=2\)
\(b,3.x-\frac{3}{5}=0\)
\(3.x=0+\frac{3}{5}\)
\(3.x=\frac{3}{5}\)
\(x=\frac{3}{5}:3\)
\(x=\frac{1}{5}\)
\(c,\frac{-2}{3}.x-\frac{1}{3}.\left(2.x-3\right)=\frac{3}{2}\)
\(\frac{-2}{3}.x-\frac{2}{3}.x+1=\frac{3}{2}\)
\(\left(\frac{-2}{3}-\frac{2}{3}\right).x=\frac{3}{2}-1\)
\(-\frac{4}{3}.x=\frac{1}{2}\)
\(x=\frac{1}{2}:\left(\frac{-4}{3}\right)\)
\(x=\frac{-3}{8}\)
Học tốt
Đáp án cần chọn là: A
Ta có (x−4).1000=0nên x–4=0(vì 1000≠0)
Suy ra
x=0+4
x=4.
Vậy x=4.