Question

Answer 1

a. \(x\ne4,-4\)

b.\(M=\left(\dfrac{4\left(x+4\right)-4\left(x-4\right)}{\left(x-4\right)\left(x+4\right)}\right).\left(\dfrac{\left(x+4\right)^2}{32}\right)\)

\(M=\left(\dfrac{4x+16-4x+16}{\left(x-4\right)\left(x+4\right)}\right).\left(\dfrac{\left(x+4\right)^2}{32}\right)\)

\(M=\left(\dfrac{32}{\left(x-4\right)\left(x+4\right)}\right).\left(\dfrac{\left(x+4\right)^2}{32}\right)\)

\(M=\dfrac{x+4}{x-4}\)

\(\dfrac{1}{3}=\dfrac{x+4}{x-4}\)

\(x-4=3\left(x+4\right)=3x+12\)

\(2x=-16\Leftrightarrow x=-8\)

Answer 2

c) \(M=\dfrac{x+4}{x-4}=1\) ⇔\(x+4=x-4\) ⇔\(8=0\) (vô lý)

- Vậy x∈∅