Câu 19: B

Câu 20: A

\(1,\Leftrightarrow x^2-10x+25=0\Leftrightarrow\left(x-5\right)^2=0\Leftrightarrow x=5\left(B\right)\\ 2,Giống.1\\ 3,=5x^2\left(B\right)\\ 4,x^3=x\Leftrightarrow x^3-x=0\\ \Leftrightarrow x\left(x^2-1\right)=0\\ \Leftrightarrow x\left(x-1\right)\left(x+1\right)=0\Leftrightarrow\left[{}\begin{matrix}x=0\\x=1\\x=-1\end{matrix}\right.\\ \Leftrightarrow A\)

(2x-1)^3 =-8

=>(2x-1)³=(-2)³

=>2x-1=-2

=>2x=-2+1

=>2x=-1

=>x=-1/2

x=1/2.

y=5/6.

\(3^{2x-1}=3^6:3^3\)

\(3^{2x-1}=3^{6-3}\)

\(3^{2x-1}=3^3\)

\(\Rightarrow2x-1=3\)

\(\Rightarrow2x=4\)

\(\Rightarrow x=2\)

vậy \(x=2\)

=> 3^2x-1 = 3^3 = 3^3

=> 2x-1 = 3

=> 2x = 3+1 = 4

=> x = 4:2 = 2

k mk nha

3^{2x - 1} = 3⁶ : 3³

3^{2x - 1} = 3³

=> 2x - 1 = 3

    2x = 3 + 1

    2x = 4 

      x = 4 : 2

      x = 2

Vậy x = 2

Đáp án: D

65− 4 x + 2 = 2020 0

65− 4 x + 2 =1

4 x + 2 =65-1

4 x + 2 =64

4 x + 2 =43

x + 2 =3

x =3 - 2

x =1