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x=\(\dfrac{-4.\left(-10\right)}{8}=5\).
y=\(\dfrac{-10.\left(-7\right)}{5}=14.\)
z=\(\dfrac{-7.\left(-24\right)}{14}=12.\)
a) \(\dfrac{x}{5}=\dfrac{6}{-10}\)
\(\Rightarrow\) (-10).x=5.6
\(\Leftrightarrow\) (-10).x=30
\(\Leftrightarrow x=30:\left(-10\right)\)
\(\Leftrightarrow\) x=(-3)
Vậy......................
b) \(\dfrac{x}{3}=\dfrac{4}{y}\)
\(\Rightarrow xy=3.4=12\)
Ta có: xy=12=1.12=12.1=2.6=6.2=3.4=4.3=(-1).(-12)=......( bạn tự ghi nốt)
\(\Rightarrow\)(x;y)=(1;12) (12;1) (2;6) (6;2) (3;4) (4;3) (-1;-12) (-12;-1) (-2;-6) (-6;-2) (-3;-4) (-4;-3)
Vậy.....................................
a: x/5=6/-10
=>x/5=-3/5
=>x=-3
b: =>xy=12
=>\(\left(x,y\right)\in\left\{\left(1;12\right);\left(12;1\right);\left(-1;-12\right);\left(-12;-1\right);\left(2;6\right);\left(6;2\right);\left(-2;-6\right);\left(-6;-2\right);\left(3;4\right);\left(4;3\right);\left(-3;-4\right);\left(-4;-3\right)\right\}\)
c: =>x/2=y/7=k
=>x=2k; y=7k
=>\(\left(x,y\right)\in\left\{\left(2k;7k\right);k\in Z\right\}\)
d: 2/x=x/8
=>x^2=16
=>x=4 hoặc x=-4
a) \(x\)=1 \(y\)= 12
b)\(x\)=4 \(y\)= 14
hoặc \(x\)= 6 \(y \)=21
...
\(\frac{27}{4}=\frac{-x}{3}=>x=-\frac{81}{4}\notinℤ\)
\(^{y^2=\frac{4}{9}=\left(\frac{2}{3}\right)^2=>y=\pm\frac{2}{3}\notinℤ}\)
\(\frac{27}{4}=\frac{\left(z+3\right)}{-4}=\left(z+3\right)=-27=\left(-3\right)^3=>z+3=-3=>z=-6\)
\(+)|t|-2=-54=>|t|=-52\)(vô lí)
\(+)|t|-2=54=>|t|=56=>t=\pm56\)
3. Gọi d là ƯCLN(2n + 3, 4n + 8), d ∈ N*
\(\Rightarrow\hept{\begin{cases}2n+3⋮d\\4n+8⋮d\end{cases}\Rightarrow\hept{\begin{cases}2\left(2n+3\right)⋮d\\4n+8⋮d\end{cases}\Rightarrow}\hept{\begin{cases}4n+6⋮d\\4n+8⋮d\end{cases}}}\)
\(\Rightarrow\left(4n+8\right)-\left(4n+6\right)⋮d\)
\(\Rightarrow2⋮d\)
\(\Rightarrow d\in\left\{1;2\right\}\)
Mà 2n + 3 không chia hết cho 2
\(\Rightarrow d=1\)
\(\RightarrowƯCLN\left(2n+3,4n+8\right)=1\)
\(\Rightarrow\frac{2n+3}{4n+8}\) là phân số tối giản.
a) x=\(\dfrac{5.6}{-10}=-3.\)
b) y=\(\dfrac{3.77}{-33}=-7.\)
a) x.21=6.7
x.21=42
x=42:21
x = 2
b) y . 20 = -5.28
y.20 = -140
y = (-140) : 20
y = -7
a)=>x*21=7*6
=>x*21=42
=>x=42/21
x=2
b)=>y*20=(-5)*28
=>y*20=-140
=>y=-140/20
y=-7
Giải :
\(\dfrac{x-3}{y-2}=\dfrac{3}{2}\) nên 2(x-3) = 3(y-2)
Do đó : 2x - 6 = 3y - 6 nên 2x = 3y
\(\Rightarrow\) 2x - 2y = y hay 2(x-y) = y
Nên 2.4 = y
Vậy : \(y=8;x=\dfrac{3y}{2}=\dfrac{3.8}{2}=12\)
\(\dfrac{x-3}{y-2}=\dfrac{3}{2}\)
\(\Rightarrow\left(x-3\right)\cdot2=3\cdot\left(y-2\right)\)
\(\Rightarrow2x-6=3y-6\)
\(\Rightarrow2x=3y\)
\(\Rightarrow\dfrac{x}{y}=\dfrac{3}{2}\)
mà x - y = 4
\(\Rightarrow\left\{{}\begin{matrix}x=4:\left(3-2\right)\cdot3=12\\y=4:\left(3-2\right)\cdot2=8\end{matrix}\right.\)
\(\text{Ta có:}\dfrac{x}{8}=\dfrac{2}{x}\)
\(\Rightarrow\dfrac{x}{8}.8x=\dfrac{2}{x}.8x\)
\(\Rightarrow x^2=16\)
\(\Rightarrow\left[{}\begin{matrix}x^2=\left(-4\right)^2\\x^2=4^2\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}x=-4^{ }\\x^{ }=4^{ }\end{matrix}\right.\)
\(\text{Vậy }x\in\left\{-4;4\right\}\)