Let a, b and c be real numbers, and simplify |a|+a=0, |ab|=ab, |c|-c=0, and simplify | B |-| A+B |-C-B |+| A-C |.

analyse

|a|+a=0, that is |a|=-a, a ≤ 0;

|ab|=ab，ab≥0，b≤0；

|c|-c=0, that is |c|=c, and c≥0.

Original formula =-b+a+b-c+b-a+c = b.

Known: (a+b)? +|b+5|=b+5, |2a-b- 1|=0, and find the value of ab.

The nonnegativity of the absolute value of the sum of squares is analyzed. If the sum of several non-negative numbers is zero, then each number is zero.

analyse

b+5 & gt； 0，(a+b)？ +b+5=b+5, which means (a+b)? =0……①

2a-b- 1=0……②

The solution is a= 1/3 and b=- 1/3.

So ab=- 1/9