MK lm bài 1:
\(\left(a-b\right)\left(a+b\right)=a^2+ab-ab-b^2=a^2-b^2\)
Bài 1:
\(\left(a-b\right)\left(a+b\right)=a^2+ab-ab-b^2\)
\(=a^2-b^2\)
\(\text{rảnh thấy câu 3b khá khó nên tớ giúp :v}\)
\(3x^2-6x=0\Leftrightarrow3x^2=6x\Leftrightarrow x^2=2x\Leftrightarrow x^2-2x=0\Leftrightarrow x^2-2x+1=1\)
\(\Leftrightarrow\left(x-1\right)^2=1\Leftrightarrow\orbr{\begin{cases}x-1=1\Leftrightarrow x=2\\x-1=-1\Leftrightarrow x=0\end{cases}}\)
\(Vậy:x\in\left\{0;2\right\}\)