1) VT=(a – b + c) – (a + c)
=a-b+c-a-c
=-b=VP
2, VT=(a + b) – (b – a) + c
=a+b-b+a+c
=2a+c=VP
3) VT=-(a + b – c) + (a – b – c)
=-a-b+c+a-b-c
=-2b=VP
4) VT=a(b + c) – a(b + d)
=ab+ac-ab-ad
=ac-ad
=a(c-d)=VP
5) VT=a(b – c) + a(d + c)
=ab-ac+ad+ac
=ab+ad
=a.(b+d)=VP