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a. Chu vi là \(\left(12+5\right).2=34\left(m\right)\)
Diện tích là \(12.5=60\left(m^2\right)=600000\left(cm^2\right)\)
b. Cần lát \(600000:\left(40.40\right)=375\) viên gạch
3x . 2 + 15 = 33
3x . 2 = 33 - 15 = 18
3x = 18 : 2 = 9 = 32
=> x = 2
\(\Leftrightarrow164-4\left(x-5\right)=80\\ \Leftrightarrow4\left(x-5\right)=84\\ \Leftrightarrow x-5=21\Leftrightarrow x=26\)
\(\frac{2^{15}\cdot9^4}{6^3.8^3}=\frac{2^{15}.3^8}{2^3.3^3.2^9}=\frac{2^{15}.3^8}{2^{12}.3^3}=2^3.3^5=8.243=1944\)
200 : [ 100 - ( 52. 20100 +50 ) ] + ( 72 - 6. 23 )2021
= 200 : [ 100 - ( 25 . 1 + 50 ) ] + ( 49 - 6 . 8 ) 2021
= 200 : [ 100 - ( 25 + 50 ) ] + ( 49 - 48 ) 2021
= 200 : [ 100 - 75 ] + 12021
= 200 : [ 100 - 75 ] + 1
= 200 : 25 + 1
= 8 + 1
= 9
\(200:[100-\left(5^2.2021^0+50\right)]+\left(7^2-6.2^3\right)^{2021}\)
\(200:[100-\left(25+50\right)]+\left(49-48\right)^{2021}\)
\(200:25+1\)
=8+1=9
\(\left|x+\frac{4}{15}\right|-\left|-3,75\right|=-\left|-2,15\right|\)
=> \(\left|x+\frac{4}{15}\right|-3,75=-2,15\)
=> \(\left|x+\frac{4}{15}\right|=-2,15+3,75\)
=> \(\left|x+\frac{4}{15}\right|=1,6=\frac{8}{5}\)
=> \(\orbr{\begin{cases}x+\frac{4}{15}=\frac{8}{5}\\x+\frac{4}{15}=\frac{-8}{5}\end{cases}}\)=> \(\orbr{\begin{cases}x=\frac{4}{3}\\x=\frac{-28}{15}\end{cases}}\)
1: \(\dfrac{x}{5}=-\dfrac{12}{10}\)
=>\(\dfrac{x}{5}=-\dfrac{6}{5}\)
=>x=-6
2: \(\dfrac{-1}{3}=\dfrac{3}{x}\)
=>\(x=\dfrac{3\cdot3}{-1}=-9\)
3: \(\dfrac{-x}{-12}=\dfrac{9}{4}\)
=>\(\dfrac{x}{12}=\dfrac{9}{4}\)
=>\(\dfrac{x}{12}=\dfrac{27}{12}\)
=>x=27
4: \(\dfrac{8}{7}=\dfrac{16}{-x}\)
=>\(\dfrac{16}{-x}=\dfrac{16}{14}\)
=>-x=14
=>x=-14
5:
ĐKXĐ: x<>0
\(\dfrac{3}{5}=-\dfrac{9}{x}\)
=>\(x=\dfrac{-5\cdot9}{3}=-5\cdot3=-15\)(nhận)
6:
ĐKXĐ: x<>9
\(\dfrac{4}{5}=\dfrac{-12}{x-9}\)
=>\(x-9=\dfrac{5\cdot\left(-12\right)}{4}=\dfrac{-60}{4}=-15\)
=>x=-15+9=-6(nhận)
7: \(\dfrac{1}{6}=\dfrac{x+3}{18}\)
=>\(x+3=18\cdot\dfrac{1}{6}=3\)
=>x=3-3=0
8: ĐKXĐ: x<>7
\(\dfrac{x-7}{25}=\dfrac{9}{x-7}\)
=>\(\left(x-7\right)\left(x-7\right)=9\cdot25\)
=>\(\left(x-7\right)^2=15^2\)
=>\(\left[{}\begin{matrix}x-7=15\\x-7=-15\end{matrix}\right.\)
=>\(\left[{}\begin{matrix}x=22\left(nhận\right)\\x=-8\left(nhận\right)\end{matrix}\right.\)
9: \(\dfrac{x}{6}=\dfrac{x-1}{5}\)
=>6(x-1)=5x
=>6x-6=5x
=>6x-5x=6
=>x=6
10: ĐKXĐ \(x\notin\left\{0;-1\right\}\)
\(\dfrac{1}{x+1}=\dfrac{2}{3x}\)
=>\(3x\cdot1=2\left(x+1\right)\)
=>3x=2x+2
=>3x-2x=2
=>x=2(nhận)