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?