Question

Tìm x:

a, \(\frac{-1}{5}\) ≤ \(\frac{x}{8}\) ≤ \(\frac{1}{4}\)

b, \(\frac{x+46}{20}\) = \(x\frac{2}{5}\)

 

Answer 1

a) \(\frac{-1}{5}\le\frac{x}{8}\le\frac{1}{4}\)

\(\frac{-8}{40}\le\frac{5x}{40}\le\frac{10}{40}\)

\(\Rightarrow-8\le5x\le10\)

\(\Rightarrow x\in\left\{-5;0;5;10\right\}\)

5.x = - 5

x = -5 ÷ 5 = -1

5.x = 0

=> x = 0

5.x = 5

=> x = 1

5.x = 10

=> x = 2

Vậy, \(x\in\left\{-1;0;1;2\right\}\)

Câu b) mình không biết làm, bạn thông cảm nha!!!

Cbht

Answer 2

a. \(-\frac{1}{5}\le\frac{x}{8}\le\frac{1}{4}\)

<=> \(-\frac{8}{40}\le\frac{5x}{40}\le\frac{10}{40}\)

<=> -8 \(\le\)5x \(\le\)10

<=> x + 5 \(\in\){\(\pm\)8;\(\pm\)7; \(\pm\)6;\(\pm\)5;\(\pm\)4;\(\pm\)3;\(\pm\)2; \(\pm\)1; 0; 9;10}

<=> x \(\in\left\{3;-13;2;-12;1;-11;0;-10;-1;-9;-2;-8;-3;-7;-4;-6;-5;4;5\right\}\)

b. \(\frac{x+46}{20}=x\frac{2}{5}\)

<=> 5x + 230 = 40x

<=> 35x = 230

<=> x = \(\frac{46}{7}\)

Answer 3

Câu a sai nha !!! Mình sửa lại sau chỗ 

-8 \(\le\)5x\(\le\)10

<=> x \(\in\){0; \(\pm\)1;2}

Answer 4

b)\(\frac{x+46}{20}=x\frac{2}{5}\)                                                \(\Rightarrow x+46=20x+8\)

\(\Rightarrow\frac{x+46}{20}=\frac{5x+2}{5}\)                                   \(\Rightarrow x-20x=8-46\)

\(\Rightarrow\frac{x+46}{20}=\frac{\left(5x+2\right)4}{20}\)                            \(\Rightarrow-19x=-38\)

                                                                                         \(\Rightarrow x=\frac{-38}{-19}=2\)