Question

Tìm x biết:x/-3=4/y

b)2/x=y/-9

c)x/3=y/7

Answer 1

a;\(\frac{x}{-3}=\frac{4}{y}\)

\(\Rightarrow xy=-12\)

\(\Rightarrow x;y\inƯ\left(-12\right)=\left\{\pm1;\pm2;\pm3;\pm4;\pm6;\pm12\right\}\)

Xét bảng 

x	1	-1	2	-2	3	-3	12	-12	6	-6	4	-4
y	-12	12	-6	6	-4	4	-1	1	-2	2	-3	3

Vậy.................................................

b,\(\frac{2}{x}=\frac{y}{-9}\)

\(\Rightarrow xy=-18\)

\(\Rightarrow x;y\inƯ\left(-18\right)=\left\{\pm1;\pm2;\pm3;\pm6;\pm9;\pm18\right\}\)

Xét bảng

x	1	-1	2	-2	3	-3	6	-6	9	-9	18	-18
y	-18	18	-9	9	-6	6	-3	3	-2	2	-1	1

Vậy...................................

c;\(\frac{x}{3}=\frac{y}{7}\)

\(\Rightarrow xy=21\)

\(\Rightarrow x;y\inƯ\left(21\right)=\left\{\pm1;\pm3;\pm7;\pm21\right\}\)

Xét bảng

x	1	-1	3	-3	7	-7	21	-21
y	21	-21	7	-7	3	-3	1	-1

Vậy..........................