x² - 4x - y² + 4

= (x² - 4x + 4) - y²

= (x - 2)² - y²

= (x - y - 2)(x + y - 2)

(x - y - 2)(x + y - 2)

\(=x\left(a-b\right)-\left(a^2-2ab+b^2\right)=\)

\(=\left(a-b\right)x-\left(a-b\right)^2=\)

\(=\left(a-b\right)\left[x-\left(a-b\right)\right]=\left(a-b\right)\left(x-a+b\right)\)

14 The fatter she gets, the more tired she feels.
15 The older he gets, the less he wants to travel.
16 The more difficult the games are, the more excited the children are.
17 The faster people dive, the more accidents happen.
18 The more I meet him, the more I hate him.
19 The less time my boss is pressed for, the better he works.
20 The more money he has, the more he wants to spend.
21 The more books you read, the more knowledge you will have.
22 The more he speaks, the more people feel bored.
23 The more the economy grows, the better people's living conditions become.
24 The farther they travel, the more things people learn.

\(x^2-xy+x-y\)

\(=x\left(x-y\right)+\left(x-y\right)\)

\(=\left(x+1\right)\left(x-y\right)\)

\(x^2-xy+x-y\)

\(=x\left(x-y\right)+\left(x-y\right)\)

\(=\left(x+1\right)\left(x-y\right)\)

Bạn xem lại đề

\(3\left(x+4\right)-x^2-4x\)

\(\Leftrightarrow3\left(x+4\right)-x\left(x+4\right)\)

\(\Leftrightarrow\left(3-x\right)\left(x+4\right)\)

\(=\left(x-y\right)\left(x+y\right)-10\left(x+y\right)=\)

\(=\left(x+y\right)\left(x-y-10\right)\)

= (x - y). (x + y) - 10 ( x - y)

= [( x + y) - 10)] . ( x - y)

  \(x^2\).(\(x\) - 1) + 16.( 1 - \(x\))

= \(x^2\).(\(x-1\)) - 16.( \(x-1\))

= (\(x\) - 1).(\(x^2\) - 16)

= (\(x\) - 1).(\(x\)² - 4²)

= (\(x\) - 1).(\(x\) - 4)(\(x\) + 4)