Bn tính máy tính là ra

ta có:

\(4\frac{2}{7}=4+\frac{2}{7}\)

\(4\frac{2}{7}=\left(4+\frac{2}{7}\right)\cdot3=4\cdot3+\frac{2}{7}\cdot3=12+\frac{6}{7}=12\frac{6}{7}\)

x.\(2\frac{3}{14}\)+ x.\(3\frac{2}{7}\)= 5 - \(2\frac{3}{4}\)

x.\(\frac{31}{14}\)+ x.\(\frac{23}{7}\)=5 -\(\frac{11}{4}\)

x (\(\frac{31}{14}\)+ \(\frac{23}{7}\) = \(\frac{20}{4}\)- \(\frac{11}{4}\)

x ( \(\frac{31}{14}\)+ \(\frac{46}{14}\))=\(\frac{9}{4}\)

x\(\frac{11}{2}\)                =\(\frac{9}{4}\)

x                           =\(\frac{9}{4}\):\(\frac{11}{2}\)

x                          =\(\frac{9}{4}\). \(\frac{2}{11}\)

x                          =\(\frac{9}{2.11}\)

x                          =\(\frac{9}{22}\)

a) \(\frac{2^{12}x3^5-4^6.9^2}{\left(2^2x3\right)^6+8^4x3^5}=\frac{2^{12}x3^5+\left(2^2\right)^6x\left(3^2\right)^2}{2^{12}x3^6+\left(2^3\right)^4x3^5}\)

\(=\frac{2^{12}x3^5-2^{12}x3^4}{2^{12}x3^6+2^{12}x3^5}=\frac{2^{12}x3^4x\left(3-1\right)}{2^{12}x3^5x\left(3+1\right)}\)

\(=\frac{2}{3.4}=\frac{1}{3.2}=\frac{1}{6}\)

b) \(\frac{1}{9x10}-\frac{1}{8x9}-\frac{1}{7x8}-\frac{1}{6x7}-\frac{1}{5x6}-\frac{1}{4x5}-\frac{1}{3x4}-\frac{1}{2x3}-\frac{1}{1x2}\)

\(=-\left(\frac{1}{1x2}+\frac{1}{2x3}+\frac{1}{3x4}+\frac{1}{4x5}+\frac{1}{5x6}+\frac{1}{6x7}+\frac{1}{7x8}+\frac{1}{8x9}+\frac{1}{9x10}\right)\)

\(=-\left(1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+...+\frac{1}{9}-\frac{1}{10}\right)\)

\(=-\left(1-\frac{1}{10}\right)\)

\(=\frac{-9}{10}\)

sorry bn nha! mk ko bk lm phần c

trả lời :

a) 1/6

b)-9/10

a, \(\overline{3x}+\overline{x3}=11\cdot11\)

\(\overline{3x}+\overline{x3}=121\)

\(33+\overline{xx}=121\)

\(\overline{xx}=121-33\)

\(\overline{xx}=88\)

\(\Rightarrow x=8\).

b, \(\left(x+1\right)+\left(x+4\right)+\left(x+7\right)+...+\left(x+28\right)=195\)

1 + 4 + 7 + ... +28 là dãy số cách đều

Số số hạng : (28 - 1) : 3 + 1 = 10 (số)

Tổng dãy số : \(\dfrac{\left(28+1\right)\cdot10}{2}=145\)

Để tìm x, ta có :

\(x\cdot10+145=195\)

\(x\cdot10=195-145\)

\(x\cdot10=50\Rightarrow x=5\)

c, \(\left(x-452\right)\cdot\text{a}=\overline{aaaa}\)

\(x-452=\overline{aaaa}:a\)

\(x-452=1111\)

\(x=1111+452=1563\)

mk ko hiểu đề