Question

tìm x, biết

(x-3).(x^2+3x+9)-x.(x+2).(x-2)=1

Answer 1

\(\left(x-3\right).\left(x^2+3x+9\right)-x.\left(x+2\right).\left(x-2\right)=1\)

\(\Leftrightarrow x^3-3^3-x.\left(x^2-2^2\right)=1\)

\(\Leftrightarrow x^3-27-x^3+4x=1\)

\(\Leftrightarrow-27+4x=1\)

\(\Leftrightarrow4x=28\)

\(\Leftrightarrow x=28:4\)

\(\Leftrightarrow x=7\)

Answer 2

\(\left(x-3\right)\left(x^2+3x+9\right)-x\left(x+2\right)\left(x-2\right)=1\)

\(\Leftrightarrow x^3-27-x\left(x^2-4\right)=1\)

\(\Leftrightarrow x^3-27-x^3+4x=1\)

\(\Leftrightarrow4x=28\)

\(\Leftrightarrow x=7\)

Answer 3

<=>(x-3).(x² +3x + 9) - x(x+2)(x-2)=1

<=> x³ - 3³ -x(x²-4)=1

<=>x³-27-x³+4x=1

<=>4x=27+1

<=>4x=28

<=>x=7

Answer 4

\((x-3).(x^2+3x+9)-x.(x+2).(x-2)=1 \)

\(\Leftrightarrow x^3-3^3-x.\left(x^2-2^2\right)=1\)

\(\Leftrightarrow x^3-3^3-x^3+2^2x=1\)

\(\Leftrightarrow x^3-x^3+4x-3^3=1\)

\(\Leftrightarrow4x-27=1\)

\(\Leftrightarrow4x=1+27\)

\(\Leftrightarrow4x=28\)

\(\Leftrightarrow x=\dfrac{28}{4}\)

\(\Leftrightarrow x=7\)

Vậy \(x=7\)