|a-c| - |a+c| - |c-a| + |-c-a| = (|a-c| - |a-c|) + (|a+c| + |c+a|) = 2|a+c|
|a-b| - |b-a| = |a-b| - |a-b| = 0
А) х²-6х+3=0
Д=36-4*3=36-12=24
х₁=(6-√24)/2=(6-2√6)/2=3-√6
х₂=3+√6
б) х²+4х-7=0
Д=16+28=44
х₁=(-4-√44)/2=(-4-2√11)/2=-2-√11
х₂=-2+√11
в) х²+4х-8=0
Д=16+32=48
х₁=(-4-√48)/2=(-4-4√3)/2=-2-2√3
х₂=-2+2√3