393-(126+3X)=0

        126+3X.  =393-0

          126+3X =393

                   3X =393-126

                   3X =267

                   X.   =267 : 3

                  X.     =89

Còn câu dưới hình như đề sai

chắc cô mình cho sai đề ùi....

(3x+1)^3=-216=(-6)^3

=>3x+1=-6

=>x=...

3^x-1+5.3^x-1=162

=>3^x-1.(1+5)=162

=>3^x-1.6=162

=>3^x-1=162:6=27

=>3^x-1=3^3

=>x-1=3

=>x=4

c)
\(x^3-3.x^2.6+3.x.6^2-6^3=0\)
\(\left(x-6\right)^3=0\)
x-6=0
x=6
d)
\(x^3-3.x^2.1+3.x.1^2-1-x^3-3x-2=0\)
\(x^3-3x^2+3x-1-x^3-3x^2-2=0\)
\(-6x^2-3=0\)
\(-3\left(2x^2+1\right)=0\)
\(2x^2+1=0\)
2x²=-1
x²=1/2
x=\(\dfrac{\sqrt{2}}{2}\)

\(x=0,\)biểu thức không thỏa mãn.

\(x\ge1\) thì \(\hept{\begin{cases}3^x⋮3\\3x⋮3\end{cases}}\Rightarrow3^x-3x⋮3\)

\(\Rightarrow3^x+2-3x\)không chia hết cho 3

Mà 216 chia hết cho 3 nên vô lý.

Mình không hiểu rõ đề, bạn dùng f(x) nhé. Mình nhìn đề thành thế này.

\(3^x\times\left(3^2-1\right)=216\)

\(3^x\times\left(9-1\right)=216\)

\(3^x\times8=216\)

\(3^x=\frac{216}{8}\)

\(3^x=27\)

\(3^x=3^3\)

\(x=3\)

\(6^x=8\times3^x\)

\(\frac{6^x}{3^x}=8\)

\(\left(\frac{6}{3}\right)^x=2^3\)

\(2^x=2^3\)

\(x=3\)

\(\left(3x+1\right)^3=1\)

\(3x+1=1\)

\(3x=1-1\)

\(3x=0\)

\(x=0\)

Cảm ơn nhiều nha

a: \(27x^3-54x^2+36x-8=0\)

=>\(\left(3x\right)^3-3\cdot\left(3x\right)^2\cdot2+3\cdot3x\cdot2^2-2^3=0\)

=>\(\left(3x-2\right)^3=0\)

=>3x-2=0

=>3x=2

=>\(x=\frac23\)

b: \(x^3+15x^2+75x+125=0\)

=>\(x^3+3\cdot x^2\cdot5+3\cdot x\cdot5^2+5^3=0\)

=>\(\left(x+5\right)^3=0\)

=>x+5=0

=>x=-5

c: \(x^3-18x^2+108x-216=0\)

=>\(x^3-3\cdot x^2\cdot6+3\cdot x\cdot6^2-6^3=0\)

=>\(\left(x-6\right)^3=0\)

=>x-6=0

=>x=6

d: \(\left(x-1\right)^3-x\left(x^2+3x\right)=2\)

=>\(x^3-3x^2+3x-1-x^3-3x^2=2\)

=>\(-6x^2+3x-3=0\)

=>\(2x^2-x+1=0\)

\(\Rightarrow x^2-\frac12x+\frac12=0\)

=>\(x^2-\frac12x+\frac{1}{16}+\frac{7}{16}=0\)

=>\(\left(x-\frac14\right)^2+\frac{7}{16}=0\) (vô lý)

=>x∈∅

e: \(\left(x+1\right)^3+\left(x-2\right)^3-2x^2\left(x-1,5\right)=3\)

=>\(x^3+3x^2+3x+1+x^3-6x^2+12x-8-2x^3+3x^2=3\)

=>15x-7=3

=>15x=10

=>\(x=\frac{10}{15}=\frac23\)

3x+1+15x=216

=>18x=216-1=215

=>\(x=\frac{215}{18}\)

a)\(\left(1-x\right)^3=216\)

\(\Rightarrow1-x=6\)

\(\Rightarrow x=-5\)

b)\(3^{x+1}-3^x=162\)

\(\Rightarrow3^x\left(3-1\right)=162\)

\(\Rightarrow3^x=81\)

\(\Rightarrow3^x=3^4\)

\(\Rightarrow x=4\)

c)\(5^{x+1}-2.5^x=375\)

\(\Rightarrow5^x\left(5-2\right)=375\)

\(\Rightarrow5^x.3=375\)

\(\Rightarrow5^x=125\)

\(\Rightarrow5^x=5^3\)

\(\Rightarrow x=3\)

a) x=-5

\(a.97-7\left(x-8\right)=3\cdot2^4\)

\(97-7\left(x-8\right)=48\)

\(7\left(x-8\right)=97-48\)

\(7\left(x-8\right)=49\)

\(x-8=49:7=7\)

\(x=7+8=15\)

\(b.5x^2-74=51\)

\(5x^2=51+74=125\)

\(x^2=125:5=25\)

\(\Rightarrow x=\pm5\)

\(c.3x+2-3x=216\)

\(0x=214\)

⇒ \(x\in\) rỗng

\(5\left(3x-4\right)^3=40\)

\(\left(3x-4\right)^3=40:5=8\)

⇒ 3x - 4 = 2

⇒ 3x = 2 + 4 = 6

⇒ x = 6 : 3 = 2

a.97−7(x−8)=3⋅24

\(97 - 7 \left(\right. x - 8 \left.\right) = 48\)

\(7 \left(\right. x - 8 \left.\right) = 97 - 48\)

\(7 \left(\right. x - 8 \left.\right) = 49\)

\(x - 8 = 49 : 7 = 7\)

\(x = 7 + 8 = 15\)

\(b . 5 x^{2} - 74 = 51\)

\(5 x^{2} = 51 + 74 = 125\)

\(x^{2} = 125 : 5 = 25\)

\(\Rightarrow x = \pm 5\)

\(c . 3 x + 2 - 3 x = 216\)

\(0 x = 214\)

⇒ \(x \in\) rỗng

\(5 \left(\left(\right. 3 x - 4 \left.\right)\right)^{3} = 40\)

\(\left(\left(\right. 3 x - 4 \left.\right)\right)^{3} = 40 : 5 = 8\)

⇒ 3x - 4 = 2

⇒ 3x = 2 + 4 = 6

⇒ x = 6 : 3 = 2