s=-a-b-c+(-c)+b+a-a-b
s=a-b
S = - ( a – b – c ) + ( - c + b + a) – ( a + b)
=> S = - a + b + c - c + b + a - a - b
=> S = ( - a + a - a ) + ( b + b - b ) + ( c - c )
=> S = - a + b
=> | S | = | - a + b |
Vậy | S | = | - a + b |
@@ Học tốt@@
Chiyuki Fujito