Question

T​ìm x biết :​a) (x-2)x-3(2-x)=0​​​​)=0

​b) (x-1)²-4=0

​c) x²+8x+15=0

d) x²-x-12=0​

Answer 1

Ta có : (x - 1)² - 4 = 0

<=> (x - 1)² - 2² = 0

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

=> (x - 3)(x + 1) = 0

\(\Leftrightarrow\orbr{\begin{cases}x-3=0\\x+1=0\end{cases}}\)

\(\Leftrightarrow\orbr{\begin{cases}x=3\\x=-1\end{cases}}\)

Answer 2

Ta có \(\left(x-1\right)^2-4=0\)

<=>\(\left(x-1\right)^2-2^2=0\)

<=>\(\left(x-1-2\right)\left(x-1+2\right)=0\)

<=>\(\left(x-3\right)\left(x+1\right)=0\)

<=>\(\orbr{\begin{cases}x-3=0\\x+1=0\end{cases}}\)

<=>\(\orbr{\begin{cases}x=3\\x=-1\end{cases}}\)