Question

如果，，那么的值一定是        （    ）．

A．7

B．3

C．— 7

D．或

Answer 1

D

得a=5，得b=2.當a=5，b=2時a+b="7," 當a=-5，b=-2時a+b=-7.當a=-5，b=2時a+b=-3當a=5，b=-2時a+b=3.故選D