The directional derivative of a function F(x,y) at a point P in the direction of the unit vector- i + j is equal to -4, while the directional derivative at P in the direction of the unit vector i+ j is equal to0. The value ofF(P) is equal to:
A) 20
B) ± 2
C) i - j
D) i - j
E) 4 i - 2 j

Question

The directional derivative of a function F(x,y) at a point P in the direction of the unit vector-  i +  j is equal to -4, while the directional derivative at P in the direction of the unit vector  i+  j is equal to0. The value ofF(P) is equal to:
A) 20 
B) ± 2 
C) i - j 
D) i - j 
E) 4 i - 2 j

Quizplus · Accepted Answer

The Answer of The directional derivative of a function F(x,y) at a point P in the direction of the unit vector-  i +  j is equal to -4, while the directional derivative at P in the direction of the unit vector  i+  j is equal to0. The value ofF(P) is equal to:
A) 20 
B) ± 2 
C) i - j 
D) i - j 
E) 4 i - 2 j

The Directional Derivative of a Function F(x,y) at a Point