8x(x - 3) - 8(x - 1)(x + 1) = 20
=> 8x2 - 24x - 8(x2 - 1) - 20 = 0
=> 8x2 - 24x - 8x2 + 8 - 20 = 0
=> -24x = -12
=> x = 1/2
\(8x\left(x-3\right)-8\left(x-1\right)\left(x+1\right)=20\Leftrightarrow8x^2-24x-8\left(x^2-1\right)=20\)
\(\Leftrightarrow8x^2-24x-8x^2+8-20=0\Leftrightarrow-24x-12=0\Leftrightarrow-24x=12\Leftrightarrow x=\frac{12}{-24}=\frac{-1}{2}\)
Ngọc Vĩ:Bạn sai rồi.-24x=12 mới đúng nhé!
\(8x\left(x-3\right)-8\left(x-1\right)\left(x+1\right)=20\)
=> \(8x^2-24x-8\left(x^2-1\right)=20\)
=> \(8x^2-24x-8x^2+8=20\)
=> \(-24x=-12\)
=> \(x=\frac{1}{2}\)
8x(x-3)-8(x-1)(x+1)=20
<=> 8x2-24x-8(x2-1)=20
<=> 8x2-24x-8x2+8=20
<=> -24x+8=20
<=>-24x=20-8
<=>-24x=12
<=>x=12:-24
<=>x=-0,5
