For function f(x,y) to have maximum value at (a,b) is?

1.	For function f(x,y) to have maximum value at (a,b) is?
A.	rt s<sup>2</sup>>0 and r<0
B.	rt s<sup>2</sup>>0 and r>0
C.	rt s<sup>2</sup><0 and r<0
D.	rt s<sup>2</sup>>0 and r>0
Answer» B. rt s<sup>2</sup>>0 and r>0

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