Question

Answer 1

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

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

b) \(\Rightarrow\left(x-1\right)\left(x^2+x+8\right)=0\)

\(\Rightarrow x=1\)(do \(x^2+x+8=\left(x+\dfrac{1}{2}\right)^2+\dfrac{31}{4}>0\))

c) \(\Rightarrow\left(x-5\right)\left(x+4\right)=0\)

\(\Rightarrow\left[{}\begin{matrix}x=5\\x=-4\end{matrix}\right.\)

d) \(\Rightarrow\left(x-1\right)\left(2x-1\right)=0\)

\(\Rightarrow\left[{}\begin{matrix}x=1\\x=\dfrac{1}{2}\end{matrix}\right.\)

e) \(\Rightarrow\left(x-2\right)\left(2x-1\right)=0\)

\(\Rightarrow\left[{}\begin{matrix}x=2\\x=\dfrac{1}{2}\end{matrix}\right.\)

Answer 2

a. x² + 4x - 5 = 0

<=> x² - x + 5x - 5 = 0

<=> x(x - 1) + 5(x - 1) = 0

<=> (x + 5)(x - 1) = 0

<=> \(\left[{}\begin{matrix}x+5=0\\x-1=0\end{matrix}\right.\)

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

c. x² - x - 20 = 0

<=> x² - 5x + 4x - 20 = 0

<=> x(x - 5) + 4(x - 5) = 0

<=> (x + 4)(x - 5) = 0

<=> \(\left[{}\begin{matrix}x+4=0\\x-5=0\end{matrix}\right.\)

<=> \(\left[{}\begin{matrix}x=-4\\x=5\end{matrix}\right.\)

d. 2x² - 3x + 1 = 0

<=> 2x² - 2x - x + 1 = 0

<=> 2x(x - 1) - (x - 1) = 0

<=> (2x - 1)(x - 1) = 0

<=> \(\left[{}\begin{matrix}2x-1=0\\x-1=0\end{matrix}\right.\)

<=> \(\left[{}\begin{matrix}x=\dfrac{1}{2}\\x=1\end{matrix}\right.\)

e. 2x² - 5x + 2 = 0

<=> 2x² - 4x - x + 2 = 0

<=> 2x(x - 2) - (x - 2) = 0

<=> (2x - 1)(x - 2) = 0

<=> \(\left[{}\begin{matrix}2x-1=0\\x-2=0\end{matrix}\right.\)

<=> \(\left[{}\begin{matrix}x=\dfrac{1}{2}\\x=2\end{matrix}\right.\)

Câu b mik vẫn chx bt làm, bn thông cảm.