bài 1

A, 5*(2 chia hết cho 3 -4)= 15

B,(3x-\(2^3\))*7=\(7^4\)

C, \(45^x\)*\(45^{123}\)=45

Bài 2 : Bạn A đọc 1 quyển sách trong 3 ngày . Ngày 1 đọc được \(\frac{1}{3}\)số trang . Ngày 2 đọc được \(\frac{3}{4}\) số trang .Ngày 3 đọc 20 trang còn lại thì xong . Hỏi quyển sách có bao nhiêu trang ?

BT1: CMR:

a) \(\dfrac{1}{2^2}+\dfrac{1}{3^2}+\dfrac{1}{4^2}+...+\dfrac{1}{n^2}< 1\)

b) \(\dfrac{1}{4}+\dfrac{1}{16}+\dfrac{1}{36}+\dfrac{1}{64}+\dfrac{1}{100}+\dfrac{1}{144}+\dfrac{1}{196}< \dfrac{1}{2}\)

c) \(\dfrac{1}{3}+\dfrac{1}{30}+\dfrac{1}{32}+\dfrac{1}{35}+\dfrac{1}{45}+\dfrac{1}{47}+\dfrac{1}{50}< \dfrac{1}{2}\)

d) \(\dfrac{1}{2}-\dfrac{1}{4}+\dfrac{1}{8}-\dfrac{1}{16}+\dfrac{1}{32}-\dfrac{1}{64}< \dfrac{1}{3}\)

e) \(\dfrac{1}{3}< \dfrac{2}{3^2}+\dfrac{3}{3^3}-\dfrac{4}{3^4}+...+\dfrac{99}{3^{99}}-\dfrac{100}{3^{100}}< \dfrac{3}{16}\)

f) \(\dfrac{1}{41}+\dfrac{1}{42}+\dfrac{1}{43}+...+\dfrac{1}{79}+\dfrac{1}{80}>\dfrac{7}{12}\)

BT2: Tính tổng

a) A=\(\dfrac{1}{3}+\dfrac{1}{3^2}+\dfrac{1}{3^3}+...+\dfrac{1}{3^{100}}\)

b) E=\(1+\dfrac{1}{2}\left(1+2\right)+\dfrac{1}{3}\left(1+2+3\right)+\dfrac{1}{4}\left(1+2+3+4\right)+...+\dfrac{1}{200}\left(1+2+3+...+200\right)\)

BT3: Cho S=\(\dfrac{3}{10}+\dfrac{3}{11}+\dfrac{3}{12}+\dfrac{3}{13}+\dfrac{3}{14}\)

CMR: 1 < S < 2

1) \(\frac{2}{5}x\frac{1}{3}-\frac{2}{15}:\frac{1}{5}+\frac{3}{5}x\frac{1}{3}\)

2)\(\left(3\frac{1}{3}+2,5\right):\left(3\frac{1}{6}-4\frac{1}{5}\right)-\frac{11}{31}\)

3)\(\left[6+\left(\frac{1}{2}\right)^3-\left|-\frac{1}{2}\right|\right]:\frac{3}{12}\)

4)\(\frac{18}{37}+\frac{8}{24}+\frac{19}{37}-1\frac{23}{24}+\frac{2}{3}\)

5)\(\left(-2\right)^3x\left(\frac{3}{4}-0,25\right):\left(2\frac{1}{4}-1\frac{1}{6}\right)\)

6)\(\left(\frac{2}{5}\right)^2+5\frac{1}{2}x\left(45-2\right)+\frac{23}{4}\)

7)\(\frac{4}{9}-19\frac{1}{3}-\frac{4}{9}x39\frac{1}{3}\)

8)\(\left(-\frac{1}{2}\right)^2:\frac{1}{4}-2x\left(-\frac{1}{2}\right)^2\)

9)\(125\%x\left(-\frac{1}{2}\right)^3:\left(1\frac{5}{16}-1,5\right)+2008^0\)

giúp mình nha mai mình học rùi

1: rút gọn rồi tính

\(\left(-\dfrac{72}{40}-\dfrac{144}{60}-2\dfrac{1}{3}\right)\) : \(\left(\dfrac{45}{100}-\dfrac{25}{60}+-\dfrac{75}{25}\right)\)

2: tìm x: \(3\cdot\left(4-x\right)+\left(x+2\right)\cdot\left(1+2x\right)=7\cdot\left(1+x\right)-2x\cdot\left(2-x\right)\)

3: tìm x: \(\dfrac{2\cdot\left(1+x\right)}{3}-\dfrac{5\cdot\left(2-x\right)}{6}=1\dfrac{1}{3}-\dfrac{3\cdot\left(2x+3\right)}{4}-1\dfrac{1}{2}\cdot\left(x+1\right)\)

4: cho a= \(3+3^{2^3}+3^3+3^4+...+3^{360}\)

Rút gọn

1.\(\left(\frac{2}{45}-\frac{4}{13}-\frac{1}{3}\right):\left(\frac{3}{13}-\frac{4}{15}+\frac{2}{13}\right)\)

2.\(\frac{0,8:\left(\frac{4}{5}.1,25\right)}{0,64-\frac{1}{25}}+\frac{\left(1,08-\frac{2}{15}\right):\frac{4}{7}}{\left(6\frac{5}{9}-3\frac{1}{4}\right)2\frac{2}{17}}\)

3.\(\frac{0,4-\frac{2}{9}+\frac{2}{11}}{1,4-\frac{7}{9}+\frac{7}{11}}-\frac{\frac{1}{3}-0,25+\frac{1}{5}}{1\frac{1}{6}-0,875+0,7}\)

tính hợp lí ( nếu có thể )

\(B=\left(\frac{2}{3}-\frac{1}{4}+\frac{5}{11}\right):\left(\frac{5}{12}+1-\frac{7}{11}\right)\)

\(C=\left(-\frac{14}{33}\right).2\frac{4}{9}+\frac{48}{25}:\frac{27}{25}\)

\(D=\left(3-2\frac{1}{3}+\frac{1}{4}\right):\left(4-5\frac{1}{6}+2\frac{1}{4}\right)\)

\(G=\left(7\frac{1}{9}-2\frac{14}{15}\right):\left(2\frac{2}{3}-6\frac{2}{3}\right)-\frac{32}{45}\)

\(H=-\frac{1}{7}.\left(9\frac{1}{2}-8,75\right):\frac{2}{7}+0,625:1\frac{2}{3}\)

tính:

\(\dfrac{2}{5}x\dfrac{1}{3}-\dfrac{2}{15}:\dfrac{1}{5}+\dfrac{3}{5}x\dfrac{1}{3}\)

2)\(\left(3\dfrac{1}{3}+2,5\right):\left(3\dfrac{1}{6}-4\dfrac{1}{5}\right)-\dfrac{11}{31}\)

3)\(\left[6+\left(\dfrac{1}{2^{ }}\right)^3-\left|-\dfrac{1}{2}\right|\right]:\dfrac{3}{12}\)

4)\(\dfrac{18}{37}+\dfrac{8}{24}+\dfrac{19}{37}-1\dfrac{23}{24}+\dfrac{2}{3}\)

5) \(\left(-2\right)^3x\left(\dfrac{3}{4}-0,25\right):\left(2\dfrac{1}{4}-1\dfrac{1}{6}\right)\)

6)\(\left(\dfrac{2}{5}\right)^2+5\dfrac{1}{2}x\left(45-2\right)+\dfrac{23}{-4}\)

7)\(\dfrac{4}{9}-19\dfrac{1}{3}-\dfrac{4}{9}x39\dfrac{1}{3}\)

8)\(\left(-\dfrac{1}{2}\right)^2:\dfrac{1}{4}-2x\left(-\dfrac{1}{2}\right)^2\)

9)\(125\%x\left(-\dfrac{1}{2}\right)^3:\left(1\dfrac{5}{16}-1,5\right)+2008^0\)

giúp mình nha mai mình học rùi