đỏ chót

1.C

2.A

3. (x - 1)(x - 2)(x + 1) = 0

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

đúng đúng

a. x² - 8x

= x(x - 8)

b. x² - xy - 6x + 6y

= x(x - y) - 6(x + y)

= (x - 6)(x - y)

a. (2x - 3)² - 49 = 0

<=> (2x - 3)² = 7²

<=> 2x - 3 = 7

<=> 2x = 10

<=> x = 5

b. 2x(x - 5) - 7(5 - x) = 0

<=> 2x(x - 5) + 7(x - 5) = 0

<=> (2x + 7)(x - 5) = 0

<=> \(\left[{}\begin{matrix}2x+7=0\\x-5=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=-3,5\\x=5\end{matrix}\right.\)

c. x² - 3x - 10 = 0

<=> x² - 5x + 2x - 10 = 0

<=> x(x - 5) + 2(x - 5) = 0

<=> (x + 2)(x - 5) = 0

<=> \(\left[{}\begin{matrix}x+2=0\\x-5=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=-2\\x=5\end{matrix}\right.\)

ghê

4 . 4³ = 4^{3 + 1} = 4⁴ = 256