a: =>y/15=-2/3

hay y=-10

b: 2/x=x/18

nên \(x^2=36\)

hay \(x\in\left\{6;-6\right\}\)

c: x/9=16/x

nên \(x^2=144\)

hay \(x\in\left\{12;-12\right\}\)

a)x=-10
b)x=-6

c)x=-12 nhé

giúp mk với

Có khác gì đâu bn

khác gì vậy

\(\frac{7}{-9}=\frac{-21}{27}=\frac{-42}{54}\)

vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv

\(\dfrac{4}{x}=\dfrac{y}{21}=\dfrac{28}{49}=\dfrac{28:7}{49:7}=\dfrac{4}{9}\\ Vậy:x=\dfrac{4.9}{4}=9\\ y=\dfrac{4.21}{9}=\dfrac{28}{3}\)

\(\dfrac{x}{2}=\dfrac{3}{y}\\ \Leftrightarrow x.y=2.3=6\\ Vậy:\left[{}\begin{matrix}\left(x;y\right)=\left(1;6\right)=\left(6;1\right)\\\left(x;y\right)=\left(2;3\right)=\left(3;2\right)\end{matrix}\right.\)

\(3,\\ \dfrac{42}{54}=\dfrac{42:6}{54:6}=\dfrac{7}{9}\\ \dfrac{42}{54}=\dfrac{7}{x}=\dfrac{7}{9}\\ Vậy:x=\dfrac{7.9}{7}=9\)

a: \(\left(x,y\right)\in\left\{\left(1;-21\right);\left(-21;1\right);\left(-1;21\right);\left(21;-1\right);\left(3;-7\right);\left(-7;3\right);\left(-3;7\right);\left(7;-3\right)\right\}\)

b: \(\Leftrightarrow\left(x,y-3\right)\in\left\{\left(1;-6\right);\left(-6;1\right);\left(2;-3\right);\left(-3;2\right);\left(-2;3\right);\left(3;-2\right);\left(6;-1\right);\left(-1;6\right)\right\}\)

hay \(\left(x,y\right)\in\left\{\left(1;-3\right);\left(-6;4\right);\left(2;0\right);\left(-3;-1\right);\left(-2;6\right);\left(3;1\right);\left(6;2\right);\left(-1;9\right)\right\}\)

a: x/2=-5/y

=>xy=-10

=>\(\left(x,y\right)\in\left\{\left(1;-10\right);\left(-10;1\right);\left(-1;10\right);\left(10;-1\right);\left(2;-5\right);\left(-5;2\right);\left(-2;5\right);\left(5;-2\right)\right\}\)

b: =>xy=12

mà x>y>0

nên \(\left(x,y\right)\in\left\{\left(12;1\right);\left(6;2\right);\left(4;3\right)\right\}\)

c: =>(x-1)(y+1)=3

=>\(\left(x-1;y+1\right)\in\left\{\left(1;3\right);\left(3;1\right);\left(-1;-3\right);\left(-3;-1\right)\right\}\)

=>\(\left(x,y\right)\in\left\{\left(2;2\right);\left(4;0\right);\left(0;-4\right);\left(-2;-2\right)\right\}\)

d: =>y(x+2)=5

=>\(\left(x+2;y\right)\in\left\{\left(1;5\right);\left(5;1\right);\left(-1;-5\right);\left(-5;-1\right)\right\}\)

=>\(\left(x,y\right)\in\left\{\left(-1;5\right);\left(3;1\right);\left(-3;-5\right);\left(-7;-1\right)\right\}\)

7/x=y/27=-42/54=-7/9

7/x=-7/9 nên x=-9

y/27=-7/9=-21/27 nên y=-21

vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv

a) Ta có: \(3x-y=13\) và \(2x-4y=60\)

Mà: \(2\left(x+2y\right)=60\Rightarrow x+2y=30\) (1)

Và: \(3x-y=13\Rightarrow6x-2y=26\) (2) 

Cộng (1) với (2) theo vế ta có:

\(\left(x+6x\right)+\left(-2y+2y\right)=30+26\)

\(\Rightarrow7x=56\)

\(\Rightarrow x=8\)

Ta tìm được y:

\(8+2y=30\)

\(\Rightarrow2y=22\)

\(\Rightarrow y=11\)

Giúp mình với nhé! Mình đang cần

b) Ta có: \(5x+2y=69\) và \(4x=3y\Rightarrow4x-3y=0\)

Mà: \(5x+2y=69\Rightarrow15x+6y=207\) (1)  

\(4x-3y=0\Rightarrow8x-6y=0\) (2)

Cộng (1) và (2) theo vế ta có:

\(\left(15x+8x\right)+\left(6y-6y\right)=207+0\)

\(\Rightarrow23x=207\)

\(\Rightarrow x=\dfrac{207}{23}\)

\(\Rightarrow x=9\)

Ta tìm được y:

\(4\cdot9=3\cdot y\)

\(\Rightarrow3y=36\)

\(\Rightarrow y=\dfrac{36}{3}\)

\(\Rightarrow y=12\)