求问涛涛30-36

Q36:

If x² + y² = 1, is x + y = 1?

(1)   xy = 0

(2) y = 0

A. Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient.

B. Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient.

C. BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.

D. EACH statement ALONE is sufficient.

E. Statements (1) and (2) TOGETHER are NOT sufficient.

                                                                                                  Answer: E

xy=0,结合x^2+y^2=1可知x,y其中一个为零,但另一个可为(+-1)

y=0,x=+-1