Question

Tính nhanh \(x^2-x-20\) : \(x-5\)

Answer 1

\(x^2-x-20=\left(x-5\right)\left(x+4\right):\left(x-5\right)=x+4\)

Answer 2

\(x^2\)-x-20:x-5,ta có:

\(x^2-x-20=\left(x+5\right)\left(x+4\right)\)

\(\Rightarrow\left(x+5\right)\left(x+4\right):\left(x+5\right)=x+4\)