Question

Answer 1

\(a)A=2.\\ \Rightarrow3x+9=2.\\ \Leftrightarrow3x=-7.\\ \Leftrightarrow x=\dfrac{-7}{3}.\)

\(b)B=2.\\ \Rightarrow\left|x-3\right|=2.\\ \Leftrightarrow\left[{}\begin{matrix}x-3=2.\\x-3=-2.\end{matrix}\right.\)

\(\Leftrightarrow\left[{}\begin{matrix}x=5.\\x=1.\end{matrix}\right.\)

\(c)C=2.\\ \Leftrightarrow x^2-7=2.\\\Leftrightarrow x^2-7-2=0.\\ \Leftrightarrow x^2-9=0.\\ \Leftrightarrow x^2=9.\\ \Leftrightarrow\left[{}\begin{matrix}x=3.\\x=-3.\end{matrix}\right.\)

 

Answer 2

Bài 5: 

a: Đặt A=2

=>3x+9=2

=>3x=-7

hay x=-7/3

b: Đặt B=2

=>|x-3|=2

=>x-3=2 hoặc x-3=-2

=>x=5 hoặc x=1

c: Đặt C=2

=>x²-7=2

=>x²=9

=>x=3 hoặc x=-3