Question

Tìm x :

2x² - 8x = -8

-3x² + 18x - 27

Answer 1

\(2x^2-8x=-8\)

\(2x^2-8x+8=0\)

\(2\left(x^2-4x+4\right)=0\)

\(2\left(x-2\right)^2=0\)

\(\Rightarrow x-2=0\)

\(x=2\)

\(-3x^2+18x-27=0\)

\(-3\left(x^2-6x+9\right)=0\)

\(-3\left(x-3\right)^2=0\)

\(\Rightarrow x-3=0\)

\(x=3\)

Answer 2

   \(2x^2-8x=-8\)

\(\Leftrightarrow2\left(x^2-4x+4\right)=0\)

\(\Leftrightarrow2\left(x^2+2x2+2^2\right)=0\)

\(\Leftrightarrow2\left(x-2\right)^2=0\)

\(\Rightarrow x=2\)

Answer 3

\(-3x^2+18x-27=0\)

\(\Leftrightarrow-3\left(x^2-6x+9\right)=0\)

\(\Leftrightarrow-3\left(x^2-2.3.x+3^2\right)=0\)

\(\Leftrightarrow-3\left(x-3\right)^2=0\)

\(\Rightarrow x=3\)