Question

Tập hợp các giá trị x thõa mãn : \(\frac{x+4}{20}=\frac{5}{x+4}\)

Answer 1

Ta có : \(\frac{x+4}{5}=\frac{20}{x+4}\)

\(\Rightarrow\left(x+4\right).\left(x+4\right)=5.20\)

\(\Rightarrow\left(x+4\right).\left(x+4\right)=100\)

\(\Rightarrow\left(x+4\right)^2=\left(\pm10\right)^2\)

\(\Leftrightarrow\left(x+4\right)=10\)

\(\Rightarrow x=10-4\)

\(\Rightarrow x=6\)

hoặc 

\(\Leftrightarrow\left(x+4\right)=-10\)

\(\Rightarrow x=-10-4\)

\(\Rightarrow x=-14\)

Answer 2

\(\frac{x+4}{20}=\frac{5}{x+4}\)

\(\left(x+4\right)^2=100\)

\(\left(x+4\right)^2=\left(\pm10\right)^2\)

\(x+4=\pm10\)

\(x+4=10\)

                \(x=10-4\)

                \(x=6\)

\(x+4=-10\)

                \(x=-10-4\)
                \(x=-14\)

Vậy \(x\in\left\{-14;6\right\}\)

 

Answer 3

\(\frac{x+4}{20}\) = \(\frac{5}{x+4}\)

\(\Rightarrow\) (x+4)(x+4) = 5.20 =100

    (x+4)² =10²

 x+4 = 10 

             x=6

x+4 = -10

          x= -14

Vậy :............

 

Answer 4

\(\frac{x+4}{20}=\frac{5}{x+4}\)
\(\left(x+4\right)\left(x+4\right)=20.5\)
\(\left(x+4\right)^2=100\)

\(\left(x+4\right)^2=10^2\)
\(x+4=10\)
\(x=10-4\)
\(x=6\)
Hoặc : \(x+4=-10\)
\(x=-10-4\)
\(x=-14\)