Question

giải giúp mình bài này nhé

cảm ơn mọi người!

Answer 1

Ta có:

\(x^3-27-9\left(x-3\right)=\left(x-3\right)\left(x^2+3x+9\right)-9\left(x-3\right)\)

\(=\left(x-3\right)\left(x^2+3x+9-9\right)=\left(x-3\right)\left(x^2+3x\right)\)

\(=\left(x-3\right)\left(x+3\right)x=x\left(x^2-9\right)\)

Answer 2

(x^3-27)-9(x-3)=x(x^2-9)

<=>(x-3)(x^2+3x+9)-9(x-3)-x(x-3)(x+3)=0

<=>(x-3)(x^2+3x-x(x+3) )=0

<=>(x-3)(x^2+3x-x^2-3x)=0

<=>(x-3)=0

<=>x=3

Answer 3

bn tách ra là đc nhá
(x^3-27)-9(x-3)
=x^3-27-9x+27
=x^3-9x
rút x ra
=x(x^2-9)

Answer 4

b: Ta có: \(x^3-27-9\left(x-3\right)=x\left(x^2-9\right)\)

\(\Leftrightarrow x^3-27-9x+27-x^3+9x=0\)

\(\Leftrightarrow0x=0\left(luônđúng\right)\)