\(3\left(2x-1\right)+2=47\\ 3\left(2x-1\right)=47-2\\ 3\left(2x-1\right)=45\\ 2x-1=45:3\\ 2x-1=15\\ 2x=15+1\\ 2x=16\\ x=16:2\\ x=8\)

Khoảng cách AB thực tế:

    \(5\times100000=500000\left(cm\right)=5\left(km\right)\)

Đáp án A

Có duy nhất 1 số nguyên tố chẵn là số 2 bạn nhé

\(\dfrac{2x\left(x+y\right)}{2xy}=\dfrac{x+y}{y}\left(DK:x,y\ne0\right)\)

- Chia cả tử số và mẫu số cho 2x khác 0

\(\left(5^1+5^3\right)+\left(5^2+5^4\right)+...+\left(5^{21}+5^{23}\right)+\left(5^{22}+5^{24}\right)\\ =5\left(1+5^2\right)+5^2\left(1+5^2\right)+...+5^{21}\left(1+5^2\right)+5^{22}\left(1+5^2\right)\\ =5.26+5^2.26+...+5^{21}.26+5^{22}.26\\ =26.\left(5+5^2+...+5^{21}+5^{22}\right)⋮13\)

DKXD: x^2-4 khác 0; x-2 khác 0; x+2 khác 0

<=> x khác {2;-2}

b) \(A=\dfrac{x^2}{\left(x-2\right)\left(x+2\right)}-\dfrac{x}{x-2}-\dfrac{2}{x+2}\\ =\dfrac{x^2-x\left(x+2\right)-2\left(x-2\right)}{\left(x-2\right)\left(x+2\right)}\\ =\dfrac{x^2-x^2-2x-2x+4}{\left(x-2\right)\left(x+2\right)}\\ =\dfrac{-4x+4}{\left(x-2\right)\left(x+2\right)}\)

a+b=13

=> (a+b)^2=169

=> a^2+2ab+b^2=169

=> (a^2-2ab+b^2)+4ab=169

=> (a-b)^2+4.40=169

=> (a-b)^2=169-160

=> (a-b)^2=9

17-2x=108:12

17-2x=9

2x=17-9

2x=8

x=8:2

x=4

\(\dfrac{3}{4}+\dfrac{2}{3}\times\dfrac{1}{2}\\ =\dfrac{3}{4}+\dfrac{1}{3}\\ =\dfrac{9}{12}+\dfrac{4}{12}\\ =\dfrac{9+4}{12}=\dfrac{13}{12}\)

\(45\times12+23\times12+12\times32=12\times\left(45+23+32\right)\\ =12\times100=1200\)

.

\(\dfrac{2}{3}+\dfrac{2}{9}+\dfrac{7}{9}+\dfrac{4}{3}\\ =\left(\dfrac{2}{3}+\dfrac{4}{3}\right)+\left(\dfrac{2}{9}+\dfrac{7}{9}\right)\\ =\dfrac{6}{3}+\dfrac{9}{9}=2+1=3\)