Tìm X : 12 * X = 42 : 1/1
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`( 42 - x ) : 9 + 1 = 4`
`( 42 - x ) : 9 =4-1`
`( 42 - x ) : 9 =3`
`42-x=3xx9`
`42-x=27`
`x=42-27`
`x=15`
Vậy `=15`
`55 - 5 xx ( x + 1 ) = 20`
`5 xx ( x + 1 ) =55-20`
`5 xx ( x + 1 ) =35`
`x+1=35:5`
`x+1=7`
`x=7-1`
`x=6`
Vậy `x=6`
`164 - 64 : ( 12 + x ) = 160`
` 64 : ( 12 + x ) =164-160`
` 64 : ( 12 + x ) =4`
`12+x=64:4`
`12+x=16`
`x=16-12`
`x=2`
Vậy `x=2`
`@` `\text {Ans}`
`\downarrow`
`(42 - x) \div 9 + 1 = 4`
` (42 - x) \div 9 = 4 - 1`
` (42 - x) \div 9 = 3`
` 42 - x = 3 \times 9`
` 42 - x = 27`
` x = 42 - 27`
` x = 15`
______
`55 - 5 \times ( x + 1 ) = 20`
`5 \times (x+1) = 55 - 20`
`5 \times (x+1) = 35`
`x + 1 = 35 \div 5`
`x + 1 = 7`
`x = 7 - 1`
`x = 6`
______
`164 - 64 \div ( 12 + x ) = 160`
`64 \div (12 + x) = 164 - 160`
`64 \div (12 + x) = 4`
`12 + x = 64 \div 4`
`12 + x = 16`
`x = 16 - 12`
`x = 4`
`@` `\text {Kaizuu lv uuu}`
a,\(\frac{11}{12}-\left(\frac{5}{42}-x\right)=\frac{15}{28}-\frac{11}{12}\)
\(\Leftrightarrow\frac{11}{12}-\frac{5}{42}+x=\frac{15}{28}-\frac{11}{12}\)
\(\Leftrightarrow x=\frac{15}{28}-\frac{11}{12}-\frac{11}{12}+\frac{5}{42}\)
\(\Leftrightarrow x=\left(\frac{15}{28}+\frac{5}{42}\right)-\left(\frac{11}{12}+\frac{11}{12}\right)\)
\(\Leftrightarrow x=\frac{55}{84}-\frac{11}{6}\)
\(\Leftrightarrow x=\frac{-33}{28}\)
b, \(\frac{x+1}{10}+\frac{x+1}{11}+\frac{x+1}{12}=\frac{x+1}{13}+\frac{x+1}{14}\)
\(\Leftrightarrow\frac{x+1}{10}+\frac{x+1}{11}+\frac{x+1}{12}-\frac{x+1}{13}-\frac{x+1}{14}=0\)
\(\Leftrightarrow\left(x+1\right)\left(\frac{1}{10}+\frac{1}{11}+\frac{1}{12}-\frac{1}{13}-\frac{1}{14}\right)=0\)
\(\Leftrightarrow x+1=0\)
\(\Leftrightarrow x=-1\)
1/2 + 1/6 + 1/12 + 1/20 + 1/30 1/x = 41/42
5/6 + 1/x = 41/42
1/x = 41/42 - 5/6
1/x = 1/7
vậy x = 7
x + 1/2 + 1/6 + 1/12 + 1/20 + 1/30 + 1/42 = 1
x + 1/1*2 + 1/2*3 + 1/3*4 + 1/4*5 + 1/5*6 + 1/6*7 = 1
x + 1/1 - 1/2 + 1/2 - 1/3 + 1/3 - 1/4 + 1/4 - 1/5 + 1/5 - 1/6 + 1/6 - 1/7 = 1
x + 1/1 - 1/7 = 1
x + 6/7 = 1
x = 1 - 6/7
x = 1/7
x + 1/2 + 1/6 + 1/20 + 1/30 + 1/42 = 1
x + 65/84 = 1
x = 1 - 65/84
x = 19/84
1/ `|x|=10<=> x=\pm 10`
2/ `|x-8|=0<=>x-8=0<=>x=8`
3/ `7+|x|=12<=>|x|=5<=>x=\pm 5`
4/ `|x+1|=3`
$\Leftrightarrow\left[\begin{array}{1}x+1=3\\x+1=-3\end{array}\right.\\\Leftrightarrow\left[\begin{array}{1}x=3\\x=-4\end{array}\right.$
5/ `15-x=16-(14-42)`
`<=>15-x=16+28`
`<=>15-x=44`
`<=>x=-29`
6/ `210-(x-12)=168`
`<=>210-x+12=168`
`<=>222-x=168`
`<=>x=54`
ta có :
\(12\times x=42:\frac{1}{10}\)
ha y \(12\times x=42\times10=420\) nên : \(x=420:12=35\)
Vậy x = 35
\(x-\left(\dfrac{1}{2}+\dfrac{1}{6}+\dfrac{1}{12}+\dfrac{1}{20}+\dfrac{1}{30}+\dfrac{1}{42}\right)=1\)
\(x-\left(\dfrac{1}{1\times2}+\dfrac{1}{2\times3}+\dfrac{1}{3\times4}+\dfrac{1}{5\times4}+\dfrac{1}{5\times6}+\dfrac{1}{7\times6}\right)=1\)
\(x-\left(1-\dfrac{1}{2}+\dfrac{1}{2}+\dfrac{1}{3}+\dfrac{1}{3}-\dfrac{1}{4}+\dfrac{1}{4}-\dfrac{1}{5}+\dfrac{1}{5}-\dfrac{1}{6}+\dfrac{1}{6}-\dfrac{1}{7}\right)=1\)
\(x-\left(1-\dfrac{1}{7}\right)=1\)
\(x-1+\dfrac{1}{7}=1\)
\(x+\dfrac{1}{7}=1+1\)
\(x+\dfrac{1}{7}=2\)
\(x=2-\dfrac{1}{7}\)
\(x=\dfrac{14-1}{7}=\dfrac{13}{7}\)
Nguyễn Ngọc Ánh: nhầm dấu hơi nhìu nhưng c.ơn đã giải cho mik.
12 * X = 42 : 1/1
= 12 * X = 42
= X = 42 : 12
= X =3,5