a, \(\left(3x-7\right)-\left(-5-7x\right)=4x+9\)
\(\Leftrightarrow3x-7+5+7x=4x+9\)
\(\Leftrightarrow3x+7x-4x=9+7-5\)
\(\Leftrightarrow\left(3+7-6\right)x=11\Rightarrow4x=11\Rightarrow x=\frac{11}{4}\notin Z\)
Vậy : \(x\in\varnothing\)
b, \(\left(3x-7\right)-\left(-5-7x\right)=5x+8\)
\(\Leftrightarrow3x-7+5+7x=5x+8\)
\(\Leftrightarrow3x+7x-5x=8+7-5\)
\(\Leftrightarrow\left(3+7-5\right)x=10\Rightarrow5x=10\Rightarrow x=10\div5=2\in Z\)
Vậy : x = 2
c, \(\left(3x-2\right)^3=125\Leftrightarrow\left(3x-2\right)^3=5^3\)
\(\Rightarrow3x-2=5\Rightarrow3x=5+2\Rightarrow3x=7\)
\(\Rightarrow x=7\div3\Rightarrow x=\frac{7}{3}\notin Z\)
Vậy \(x\in\varnothing\)
a, (3x-7)-(-5-7x)=4x+9
3x-7+5+7x=4x+9
3x+7x-4x=9+7-5
6x=11
x=11/6(thuộc Z t/m)
Vậy...
b, (3x-7)-(-5-7x)=5x+8
3x-7+5+7x=5x+8
3x+7x-5x=8+7-5
5x=10
x=2(thuộc Z t/m)
vây...
c, (3x-2)^3=125
(3x-2)^3=5^3
3x-2=5
x=7/3(thuộc Z thỏa mãn)
Vậy...