A =   2 + 2² + 2³ + ....+ 2¹⁹+ 2²⁰

2A =         2² + 2³  +....+ 2¹⁹ + 2²⁰ + 2²¹

2A - A =   2²¹ - 2

A        = 2²¹ - 2

A = (2⁴)⁵.2 - 2

A =  \(\overline{...6}\)⁵.2 - 2

A =  \(\overline{..6}\).2  - 2

A = \(\overline{...2}\) - 2

A = \(\overline{...0}\)

\(\dfrac{1}{2}h=30phut\)

1h=60p

1/2h=60p:2=30p

\(V=6x5x8=240\left(cm^2\right)\Rightarrow B\)

Thể tích của hình hộp chữ nhật là:

       5 x 6 x 8 = 240 ( cm³)

⇒ Đáp án đúng là D

chúc bn học tốt

\(A=1+\dfrac{1}{2}+\dfrac{1}{4}+\dfrac{1}{8}+....+\dfrac{1}{1024}\)

\(2A=2+1+\dfrac{1}{2}+\dfrac{1}{4}+....+\dfrac{1}{512}\)

\(2A-A=\left(2+1+\dfrac{1}{2}+\dfrac{1}{4}+....+\dfrac{1}{512}\right)-\left(1+\dfrac{1}{2}+\dfrac{1}{4}+\dfrac{1}{8}+....+\dfrac{1}{1024}\right)\)

\(A=2-\dfrac{1}{1024}\)

\(A=\dfrac{2047}{1024}\)

\(A=1+\dfrac{1}{2}+\dfrac{1}{4}+\dfrac{1}{8}+...+\dfrac{1}{1024}\\ =1+\dfrac{1}{2^1}+\dfrac{1}{2^2}+...+\dfrac{1}{2^{10}}\\ \Rightarrow\dfrac{1}{2}A=\dfrac{1}{2}+\dfrac{1}{2^2}+\dfrac{1}{2^3}+...+\dfrac{1}{2^{11}}\\ \Rightarrow A-\dfrac{1}{2}A=1-\dfrac{1}{2^{11}}\\ \Rightarrow A=2-\dfrac{1}{2^{10}}\)

Câu C

C Vì \(0,5\%=\dfrac{0,5}{100}=\dfrac{5}{1000}\)

Rồi nha :33

(\(x\) - 5)² = 16

(\(x-5\))² = 4²

\(\left[{}\begin{matrix}x-5=4\\x-5=-4\end{matrix}\right.\)

\(\left[{}\begin{matrix}x=9\\x=1\end{matrix}\right.\)

Vậy \(x\) \(\in\) { 1; 9 }

B. 4^\(x\)  + 33 = 7²

   4\(^x\) + 33 = 49

   4\(^x\)         = 49 - 33

   4\(^x\)        = 16

   4\(^x\)        = 16

  4\(^x\)        = 4²

    \(x\)        = 2

c. 2\(^x\).4 = 128

   2\(^x\)    = 128 : 4

   2\(^x\)    = 32

   2\(^x\)    = 2⁵

   \(x\)      = 5

D, 5\(^x\) . 3 - 75 = 0

    5\(^x\).3      = 75

     5\(^x\)       = 75: 3

    5\(^x\)       = 25

   5\(^x\)        = 5²

     \(x\)       = 2

A) \(\left(x-5\right)^2=16=4^2\Rightarrow\left[{}\begin{matrix}x-5=4\\x-5=-4\end{matrix}\right.\) \(\Rightarrow\left[{}\begin{matrix}x=9\\x=1\end{matrix}\right.\)

B) \(4^x+33=7^2\Rightarrow4^x=49-33\Rightarrow4^x=16=4^2\Rightarrow x=2\)

C) \(2^x.4=128\Rightarrow2^x=32=2^5\Rightarrow x=5\)

 D) \(5^x.3-75=0\Rightarrow5^x.3=75\Rightarrow5^x=25=5^2\Rightarrow x=2\)

\(1,2\cdot35+2,56:0,8+58\\ =42+3,2+58\\ =103,2\\ \\ \left(23+15:2,5\right):14,5+17\\ =\left(23+6\right):14,5+17\\ =29:14,5+17=2+17\\ =19\)

\(1,2.3,5+2,56:0,8+58=4,2+3,2+58=7,4+58=65,4\)

\(\left\{{}\begin{matrix}x\in B\left(10\right)\\10< x< 60\end{matrix}\right.\\ \Rightarrow x\in\left\{20;30;40;50\right\}\\ \left\{{}\begin{matrix}x⋮2\\0< x< 20\end{matrix}\right.\\ \Rightarrow x\in\left\{2;4;6;8;10;12;14;16;18\right\}\)

a) 4,6,8,10,12

B)5,10,15,20,25

a) 4,6,8,10,12

B)5,10,15,20,25