c. khi và chỉ khi \(\frac{3}{5}\cdot\frac{1}{x}=\frac{1}{3}-\frac{4}{15}=\frac{1}{15}\)
\(\frac{1}{x}=\frac{1}{15}\cdot\frac{5}{3}=\frac{1}{9}\)
suy ra x=9
a,7/6x=3/5-1/30
7/6x=17/30
x=17/30:7/6
x=17/35
b,(-9/2-2x).11/7=11/4
-9/2-2x=11/4:11/7
-9/2-2x=7/4
2x=-9/2-7/4
2x=-25/4
x=-25/4:2
x=-25/8
c,9
d,x=-2
e,2.8=x.x=x2
16=x2=>x=4 hoặc -4
a,7/6x=3/5-1/30
7/6x=17/30
x=17/30:7/6
x=17/35
b,(-9/2-2x).11/7=11/4
-9/2-2x=11/4:11/7
-9/2-2x=7/4
2x=-9/2-7/4
2x=-25/4
x=-25/4:2
x=-25/8
c,9
d,x=-2
e,2.8=x.x=x2
16=x2=>x=4 hoặc -4