Question

Tìm x biết :

a) (x² + 5x)²  - 2(x²+5x) -24 = 0

b) (x+1/x)² + 2 ( x+1/x) -8 =0

c) x² - 2x - 3. |x-1| + 3 = 0

Giúp tớ với T^T !!!!

Answer 1

\(\left(x^2+5x\right)^2-2\left(x^2+5x\right)-24=0\)

\(\Rightarrow\left(x^2+5x\right)^2-2\left(x^2+5x\right).1+1-25=0\)

\(\Rightarrow\left(x^2-5x+1\right)^2-25=0\)

\(\Rightarrow\left(x^2-5x+1+5\right)\left(x^2+5x+1-5\right)=0\)

\(\Rightarrow\left(x^2-5x+6\right)\left(x^2-5x-4\right)=0\)

\(\Rightarrow\orbr{\begin{cases}x^2-5x+6=0\\x^2-5x-4=0\end{cases}}\)

TH1 : \(x^2-5x+6=0\Rightarrow\left(x-3\right)\left(x-2\right)=0\)

\(\Rightarrow\orbr{\begin{cases}x=2\\x=3\end{cases}}\)

Th2 : \(x^2-5x+4=0\Rightarrow\left(x-4\right)\left(x-1\right)=0\)

\(\Rightarrow\orbr{\begin{cases}x-4=0\\x-1=0\end{cases}\Rightarrow\orbr{\begin{cases}x=4\\x=1\end{cases}}}\)

Answer 2

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