Cho ba mặt phẳng
\(\left(\alpha\right):x+y+2z+1=0\) , \(\left(\beta\right):x+y-z+2=0\) , \(\left(\gamma\right):x-y+5=0\).
Trong các khẳng định đề sau, khẳng định nào sai?
- \(\left(\alpha\right)\perp\left(\beta\right)\)
- \(\left(\gamma\right)\perp\left(\beta\right)\)
- \(\left(\alpha\right)\) // \(\left(\gamma\right)\)
- \(\left(\alpha\right)\perp\left(\gamma\right)\)