People's education edition, the second volume of the second grade, mathematics scores, multiplication, division, addition and subtraction exercises. (Just calculating the problem or simplifying the topic of evaluation. ) 1, simplification++equals ()

A.B. C. D。

2. Calculate+-to get ()

A. 2nd century BC

3. Calculate a-b+ ()

A.b a+b c d a-b

4. If =+,then m =.

5. When the value of the fraction-is equal to zero, then x =.

6. If a>b>0, the sign of the-value is.

7. Given that A+B = 3, AB = 1, the value of+is equal to.

8. (Error-prone) Calculation:-.

9. (Error-prone) Calculation: -X- 1.

10, simplify first and then evaluate:-+,where a =.

1 1. As we all know, the distance between A and B is S kilometers. It takes M hours for Wang Gang to go from A to B, and N hours for Zhao Jun to go from B to A.. When will they meet?

12, (open question) Two scores are known: A =, B =+, where X ≠ 2. There are three conclusions as follows: ① A = B; ②A-B = 0； ③ A+B = 0。 Which one is correct? Why?