Question

Bài 1. Tính giá trị biểu thức

125%.\((\dfrac{-1}{2})^2\):\((1\dfrac{5}{16}-1,5)+2008^0\)

\(\dfrac{2}{3.5}+\dfrac{2}{5.3}+\dfrac{2}{7.9}+\dfrac{2}{9.11}+\dfrac{2}{11.13}+\dfrac{2}{13.15}\)

Bài 2. Tìm x, biết

x:\(3\dfrac{1}{15}=1\dfrac{1}{12}\)

\(\dfrac{3}{4}.x=27\)

\(x.\dfrac{1}{4}=\dfrac{5}{8}.\dfrac{2}{3}\)

\(\left(x+\dfrac{1}{4}\right):\dfrac{3}{7}=\dfrac{1}{6}\)

\(\dfrac{3}{4}-2.|2x-\dfrac{2}{3}|=2\)

\(\dfrac{2}{3}x-\dfrac{1}{2}x=\dfrac{5}{2}\)

Answer 1

có nhất thiết phải hỏi mấy bài thế này ko ?

Answer 2

125%.$(\frac{-1}{2}{)}^2$:$(1\frac{5}{16}-1,5)+{2008}^0$

$\frac{\mathrm{=1.25x0,25:(1,3125-1,5)+1}}{}$

$\frac{\mathrm{=0,3125:(-0,1875)+1}}{}$

$\frac{\mathrm{=-5/3+1}}{}$

=-2/3

vậy.......

$\frac{2}{3.5}+\frac{2}{5.7}+\frac{2}{7.9}+\frac{2}{9.11}+\frac{2}{11.13}+\frac{2}{13.15}$

\(=\dfrac{1}{3}-\dfrac{1}{5}+\dfrac{1}{5}-\dfrac{1}{7}+\dfrac{1}{7}-\dfrac{1}{9}+\dfrac{1}{9}-\dfrac{1}{11}+\dfrac{1}{11}-\dfrac{1}{13}+\dfrac{1}{13}-\dfrac{1}{15}\)

\(=\dfrac{1}{3}-\dfrac{1}{15}=\dfrac{4}{15}\)

câu này viết sai đề nhé!!!!

Bài 2. Tìm x, biết

x:$3\frac{1}{15}=1\frac{1}{12}$

$\frac{\mathrm{\backslash (\backslash Rightarrow\; x=1\backslash dfrac\{1\}\{12\}\backslash cdot3\backslash dfrac\{1\}\{15\}=\backslash dfrac\{299\}\{90\}\backslash )}}{}$

vậy

$\frac{3}{4}.x=27$

$\mathrm{\backslash (\backslash Rightarrow\; x=27:\backslash dfrac\{3\}\{4\}=36\backslash )}$

vậy.....

$x.\frac{1}{4}=\frac{5}{8}.\frac{2}{3}$

\(\Rightarrow x=\dfrac{5}{8}\cdot\dfrac{2}{3}:\dfrac{1}{4}=\dfrac{5}{3}\)

vậy........

$\left(x+\frac{1}{4}\right):\frac{3}{7}=\frac{1}{6}$

$\frac{\mathrm{\backslash (x:\backslash dfrac\{3\}\{7\}+\backslash dfrac\{1\}\{4\}:\backslash dfrac\{3\}\{7\}=\backslash dfrac\{1\}\{6\}\backslash )}}{}$

\(x:\dfrac{3}{7}=\dfrac{1}{6}-\dfrac{1}{4}:\dfrac{3}{7}\)

\(x:\dfrac{3}{7}=-\dfrac{5}{12}\)

\(x=-\dfrac{5}{12}\cdot\dfrac{3}{7}=-\dfrac{5}{28}\)

vậy............

$\frac{3}{4}-2.|2x-\frac{2}{3}|=2$

$\mathrm{\backslash (\backslash dfrac\{3\}\{4\}-4\backslash left|x-\backslash dfrac\{1\}\{3\}\backslash right|=2\backslash )}$

\(4\left|x-\dfrac{1}{3}\right|=\dfrac{3}{4}-2\)

\(4\left|x-\dfrac{1}{3}\right|=-1,25\)

\(\left|x-\dfrac{1}{3}\right|=-1,25:4=-0,3125\)(loại)

vậy.............

$\frac{2}{3}$$x-\frac{1}{2}x=\frac{5}{2}$