tìm x biết a, 15 + x = 7 ; b, x - 9 = -24 ; c, - x + 8 = - 22 giúp mình với
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Bài 1:
a) \(=\dfrac{8}{15}\left(\dfrac{7}{13}+\dfrac{6}{13}\right)=\dfrac{8}{15}.1=\dfrac{8}{15}\)
b) \(=\dfrac{3.3-7-2.4}{12}=-\dfrac{6}{12}=-\dfrac{1}{2}\)
Bài 2:
\(\dfrac{x}{2,7}=-\dfrac{2}{3,6}\Rightarrow x=\dfrac{\left(-2\right).2,7}{3,6}\Rightarrow x=-\dfrac{3}{2}\)
Bài 3:
\(\dfrac{x}{2}=\dfrac{y}{5}=\dfrac{x+y}{2+5}=-\dfrac{21}{7}=-3\)
\(\Rightarrow\left\{{}\begin{matrix}x=\left(-3\right).2=-6\\y=\left(-3\right).5=-10\end{matrix}\right.\)
Bài 6. Tìm x ϵ N biết
a) (x –15) .15 = 0
b) 32 (x –10 ) = 32
c) ( x – 5)(x – 7) = 0
d) (x – 35).35 = 35
A.\(\left(x-15\right).15=0\)
\(x-15=0:15\)
\(x-15=0\)
\(x=15+0\)
\(x=15\)
B.\(32\left(x-10\right)=32\)
\(x-10=32:32\)
\(x-10=1\)
\(x=10+1\)
\(x=11\)
`a) `
`(x-15)xx15=0`
`<=> x-15 = 0 : 15`
`<=> x-15 = 0`
`<=> x = 0 + 15`
`<=> x =15`
`b)`
`32.(x-10)=32`
`<=> x - 10 = 32:32`
`<=>x-10=1`
`<=> x = 1+10`
`<=> x =11`
`c)`
`(x-5).(x-7)=0`
`<=>` \(\left[ \begin{array}{l}x-5 = 0\\x-7=0\end{array} \right.\)
`<=>` \(\left[ \begin{array}{l}x=5\\x=7\end{array} \right.\)
`d)`
`(x-35)xx35=35`
`<=> x - 35 = 35:35`
`<=> x - 35 = 1`
`<=> x = 1+35`
`<=> x = 36`
a) |x| -14= 15 -(-27)
|x|-14 = 15+27= 42
|x| = 42 + 14 = 56
=> x= 56 và (-56)
b) (x-28) + 7 = 15
x -28 = 15 -7 = 8
x = 28 + 8 = 36
Bài 1:
a) \(\dfrac{9}{20}-\dfrac{8}{15}\times\dfrac{5}{12}\)
\(=\dfrac{9}{20}-\dfrac{2}{9}\)
\(=\dfrac{41}{180}\)
b) \(\dfrac{2}{3}\div\dfrac{4}{5}\div\dfrac{7}{12}\)
\(=\dfrac{2}{3}\times\dfrac{5}{4}\times\dfrac{12}{7}\)
\(=\dfrac{5}{6}\times\dfrac{12}{7}\)
\(=\dfrac{10}{7}\)
c) \(\dfrac{7}{9}\times\dfrac{1}{3}+\dfrac{7}{9}\times\dfrac{2}{3}\)
\(=\dfrac{7}{9}\times\left(\dfrac{1}{3}+\dfrac{2}{3}\right)\)
\(=\dfrac{7}{9}\times1\)
\(=\dfrac{7}{9}\)
Bài 2:
a) \(2\times\left(x-1\right)=4026\)
\(\left(x-1\right)=4026\div2\)
\(x-1=2013\)
\(x=2014\)
Vậy: \(x=2014\)
b) \(x\times3,7+6,3\times x=320\)
\(x\times\left(3,7+6,3\right)=320\)
\(x\times10=320\)
\(x=320\div10\)
\(x=32\)
Vậy: \(x=32\)
c) \(0,25\times3< 3< 1,02\)
\(\Leftrightarrow0,75< 3< 1,02\) ( S )
=> \(0,75< 1,02< 3\)
a, \(x\) \(⋮\) 7 ⇒ \(x\) \(\in\) A = { \(x\in\) Z/ \(x\) = 7k; k \(\in\) Z}
b, 15 \(⋮\) \(x\) + 1 đkxđ \(x\ne\) - 1
\(\Rightarrow\) \(x\) + 1 \(\in\) { -15; -5; -3; -1; 1; 3; 5; 15}
\(x\) \(\in\) { -16; -6; -4; -2; 0; 2; 4; 14}
c, (\(x\) + 6) \(⋮\) (\(x-1\)) đkxđ \(x\ne\) 1
\(x+6⋮\) \(x-1\)
\(x\) - 1 + 7 ⋮ \(x-1\)
7 ⋮ \(x-1\)
\(x-1\) \(\in\) { -7; -1; 1; 7}
\(x\) \(\in\) { -6; 0; 2; 8}
a/
\(x=7k⋮7\) (k là số nguyên dương)
b/
\(15⋮x+1\Rightarrow x+1=\left\{-15;-5;-3;-1;1;3;5;15\right\}\)
\(\Rightarrow x=\left\{-16;-6;-4;-2;0;2;4;14\right\}\)
c/
\(\dfrac{x+6}{x-1}=\dfrac{\left(x-1\right)+7}{x-1}=1+\dfrac{7}{x-1}\)
\(\left(x+6\right)⋮\left(x-1\right)\) khi \(7⋮\left(x-1\right)\Rightarrow\left(x-1\right)=\left\{-7;-1;1;7\right\}\Rightarrow x=\left\{-6;0;2;8\right\}\)
a: =>2^x=32
=>x=5
b: =>7x-11=25*25+200=825
=>7x=836
=>x=836/7
c: =>x(x^9-1)=0
=>x=0 hoặc x^9-1=0
=>x=0 hoặc x=1
a) \(x=-8\)
b) \(x=-15\)
c) \(x=-30\)
a, 15 + x = 7
X= 7-15
x= -8
b, x - 9 = -24
x= -24+9
x= -15
c, - x + 8 = - 22
-x = -22-8
-x=-30
x=30