C

C

Theo tính chất dãy tỉ số bằng nhau:

 \(\dfrac{x}{3}=\dfrac{y}{5}=\dfrac{x+y}{3+5}=\dfrac{-32}{8}=-4\)

\(\Rightarrow\left\{{}\begin{matrix}x=-12\\y=-20\end{matrix}\right.\)

\(a,x\left(y-2\right)=8\\ \Rightarrow x;\left(y-2\right)\inƯ\left(8\right)=\left\{-8;-4;-2;-1;1;2;4;8\right\}\)

Vậy \(\left(x;y\right)=\left(-8;1\right),\left(-4;0\right),\left(-2;-2\right),\left(-1;-6\right),\left(2;6\right),\left(4;4\right),\left(8;3\right)\)

\(b,\left(x-1\right)\left(y-2\right)=9\\ \Rightarrow\left(x-1\right),\left(y-2\right)\inƯ\left(9\right)=\left\{-9;-3;-1;1;3;9\right\}\)

Vậy \(\left(x;y\right)=\left(-8;1\right),\left(-2;-1\right),\left(0;-7\right),\left(2;11\right),\left(4;5\right),\left(10;3\right)\)

\(c,\left(x+1\right)\left(y-2\right)=15\\ \Rightarrow\left(x+1\right),\left(y-2\right)\inƯ\left(15\right)=\left\{-15;-1;1;15\right\}\)

Vậy \(\left(x;y\right)=\left(-16;1\right),\left(-2;-13\right),\left(0;17\right),\left(14;3\right)\)

Có: \(\frac{\frac{-1}{2}}{2x-1}=\frac{\frac{0,2}{-3}}{5}\)\(\Rightarrow\left(2x-1\right).\frac{0,2}{-3}=\frac{-1}{2}.5\Leftrightarrow\left(2x-1\right).\frac{0,2}{-3}=\frac{-5}{2}\)\(\Leftrightarrow2x-1=\frac{-75}{2}\Leftrightarrow2x=\frac{-73}{2}\Leftrightarrow x=\frac{-73}{4}\)

Vậy x=-73/4

a) Vì \(\dfrac{x}{y} = \dfrac{5}{3} \Rightarrow \dfrac{x}{5} = \dfrac{y}{3}\)

Áp dụng tính chất của dãy tỉ số bằng nhau, ta có:

\(\begin{array}{l}\dfrac{x}{5} = \dfrac{y}{3} = \dfrac{{x + y}}{{5 + 3}} = \dfrac{{16}}{8} = 2\\ \Rightarrow x = 2.5 = 10\\y = 2.3 = 6\end{array}\)

Vậy x=10, y=6

b) Vì \(\dfrac{x}{y} = \dfrac{9}{4} \Rightarrow \dfrac{x}{9} = \dfrac{y}{4}\)

Áp dụng tính chất của dãy tỉ số bằng nhau, ta có:

 \(\begin{array}{l}\dfrac{x}{9} = \dfrac{y}{4} = \dfrac{{x - y}}{{9 - 4}} = \dfrac{{ - 15}}{5} =  - 3\\ \Rightarrow x = ( - 3).9 =  - 27\\y = ( - 3).4 =  - 12\end{array}\)

Vậy x = -27, y = -12.

áp dụng t/c dãy tỉ só bằng nhau đúng ko

b

yx(15+35)=150

yx50          =150

y                =150:50=3

yx5=713-173

yx5=540

y   =540:5=108

a. y x (15+35)=150

y x 50 =150

y         = 150 : 50

y         = 3

b.    y x 5    = 713-173

       y x 5    = 540

       y          =540:5

       y          = 108

15^x : 5^y = 45^y

=> 15^x = 45^y * 5^y = (45 *5)^y = 225^y 

=> 15^x = 225^y 

=> 15^x  - 225^y = 0

=> x = 0, y = 0  

\(15^x:5^y=45^y\)

\(\Rightarrow\)\(15^x=45^y.5^y\)

\(\Rightarrow\)\(15^x=\left(45.5\right)^y\)

\(\Rightarrow\)\(15^x=225^y\)

\(\Rightarrow\)\(15^x=\left(15^2\right)^y\)

\(\Rightarrow\)\(15^x=15^{2y}\)

\(\Rightarrow\)\(x=2y\)

\(\Rightarrow\)\(\frac{x}{y}=2\)