K
Khách

Hãy nhập câu hỏi của bạn vào đây, nếu là tài khoản VIP, bạn sẽ được ưu tiên trả lời.

6 tháng 9 2016

a. -3/4 x 12/-5 x (-25/6)=-15/2

b. -2 x -38/21 x -7/4 x (-3/8)=-19/8

c. (11/12: 33/16) x 3/5=4/15

d. 7/23 x [(-8/6)- 45/18]=-7/6

31 tháng 12 2018

a. -3/4 x 12/-5 x (-25/6)=-15/2

b. -2 x -38/21 x -7/4 x (-3/8)=-19/8

c. (11/12: 33/16) x 3/5=4/15

d. 7/23 x [(-8/6)- 45/18]=-7/6

2. Tham khảo thêm tại đây nha bạn

https://hoc24.vn/hoi-dap/question/417550.html

5 tháng 8 2017

1. So sánh

a) \(25^{50}\)\(2^{300}\)

\(25^{50}=25^{1.50}=\left(25^1\right)^{50}=25^{50}\)

\(2^{300}=2^{6.50}=\left(2^6\right)^{50}=64^{50}\)

\(25< 64\) nên \(25^{50}< 64^{50}\)

Vậy \(25^{50}< 2^{300}\)

b) \(625^{15}\)\(12^{45}\)

\(625^{15}=625^{1.15}=\left(625^1\right)^{15}=625^{15}\)

\(12^{45}=12^{3.15}=\left(12^3\right)^{15}=1728^{15}\)

\(625< 1728\) nên \(625^{15}< 1728^{15}\)

Vậy \(625^{15}< 12^{45}\)

5 tháng 8 2017

1.So sánh

a)\(25^{50}\)\(2^{300}\)

Ta có : \(2^{300}=\left(2^6\right)^{50}=64^{50}\)

\(25^{50}< 64^{50}\) nên \(25^{50}< 2^{300}\)

b)\(625^{15}\)\(12^{45}\)

Ta có : \(12^{45}=\left(12^3\right)^{15}=1728^{15}\)

\(625^{15}< 1728^{15}\) nên \(625^{15}< 12^{45}\)

21 tháng 6 2017

1)

a) \(0,25^x\cdot12^x=243\)

\(\Leftrightarrow\left(0,25\cdot12\right)^x=3^5\)

\(\Leftrightarrow3^x=3^5\)

\(\Leftrightarrow x=5\)

Vậy \(x=5\)

b) \(38^y:19^y=512\)

\(\Leftrightarrow2y\cdot y=512\)

\(\Leftrightarrow2y^2=512\)

\(\Leftrightarrow y^2=256\)

\(\Leftrightarrow\left[{}\begin{matrix}y=16\\y=-16\end{matrix}\right.\)

Vậy \(y_1=-16;y_2=16\)

2)

a) \(3^x+3^{x+2}=2430\)

\(\Leftrightarrow\left(1+3^2\right)\cdot3^x=2430\)

\(\Leftrightarrow\left(1+9\right)\cdot3^x=2430\)

\(\Leftrightarrow10\cdot3^x=2430\)

\(\Leftrightarrow3^x=243\)

\(\Leftrightarrow3^x=3^5\)

\(\Leftrightarrow x=5\)

Vậy \(x=5\)

b) \(2^{x+3}-2^x=224\)

\(\Leftrightarrow\left(2^3-1\right)\cdot2^x=224\)

\(\Leftrightarrow\left(8-1\right)\cdot2^x=224\)

\(\Leftrightarrow7\cdot2^x=224\)

\(\Leftrightarrow2^x=32\)

\(\Leftrightarrow2^x=2^5\)

\(\Leftrightarrow x=5\)

Vậy \(x=5\)

3)

a) \(\left(x-\dfrac{1}{4}\right)^2=\dfrac{4}{9}\)

\(\Leftrightarrow x-\dfrac{1}{4}=\pm\dfrac{2}{3}\)

\(\Leftrightarrow\left[{}\begin{matrix}x-\dfrac{1}{4}=\dfrac{2}{3}\\x-\dfrac{1}{4}=-\dfrac{2}{3}\end{matrix}\right.\)

\(\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{2}{3}+\dfrac{1}{4}\\x=-\dfrac{2}{3}+\dfrac{1}{4}\end{matrix}\right.\)

\(\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{11}{12}\\x=-\dfrac{5}{12}\end{matrix}\right.\)

Vậy \(x_1=\dfrac{11}{12};x_2=-\dfrac{5}{12}\)

b) \(\left(x+0,7\right)^3=-27\)

\(\Leftrightarrow\left(x+\dfrac{3}{10}\right)^3=\left(-3\right)^3\)

\(\Leftrightarrow x+\dfrac{3}{10}=-3\)

\(\Leftrightarrow x=-3-\dfrac{3}{10}\)

\(\Leftrightarrow x=-\dfrac{37}{10}\)

Vậy \(x=-\dfrac{37}{10}\)

4)

a) \(\left(\dfrac{2}{5}-3x\right)^2=\dfrac{9}{25}\)

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

\(\Leftrightarrow\left[{}\begin{matrix}\dfrac{2}{5}-3x=\dfrac{3}{5}\\\dfrac{2}{5}-3x=-\dfrac{3}{5}\end{matrix}\right.\)

\(\Leftrightarrow\left[{}\begin{matrix}3x=-\dfrac{1}{5}\\3x=1\end{matrix}\right.\)

\(\Leftrightarrow\left[{}\begin{matrix}x=-\dfrac{1}{15}\\x=\dfrac{1}{3}\end{matrix}\right.\)

Vậy \(x_1=-\dfrac{1}{15};x_2=\dfrac{1}{3}\)

b) \(\left(\dfrac{2}{3}x-\dfrac{1}{3}\right)^5=\dfrac{1}{243}\)

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

\(\Leftrightarrow2x-1=1\)

\(\Leftrightarrow2x=1+1\)

\(\Leftrightarrow2x=2\)

\(\Leftrightarrow x=1\)

Vậy \(x=1\)

21 tháng 6 2017

1. a) \(0,25^x.12^x=243\)

\(\Rightarrow\left(0,25.12\right)^x=243\)

\(\Rightarrow3^x=3^5\)

\(\Rightarrow x=5\)

Vậy \(x=5.\)

b) \(38^y:19^y=512\)

\(\Rightarrow\left(38:19\right)^y=512\)

\(\Rightarrow2^y=2^9\)

\(\Rightarrow y=9\)

Vậy \(y=9.\)

2) a) \(3^x+3^{x+2}=2430\)

\(\Rightarrow3^x\left(1+9\right)=2430\)

\(\Rightarrow3^x=243=3^5\)

\(\Rightarrow x=5\)

Vậy x=5.

b) \(2^{x+3}-2^x=224\)

\(\Rightarrow2^x\left(8-1\right)=224\)

\(\Rightarrow2^x=32=2^5\)

\(\Rightarrow x=5\)

Vậy x=5.

Bài 3: dễ tự làm.