The gradient is , and at we have . The directional derivative in the direction of the unit vector is . So if you know that this directional derivative is equal to some value , you want to solve the system of equations:
for .
In what direction does the directional derivative for f(x, y) = x2y at (1, 1) have
A. Value 1?
B. Value -2?
C. Is there a direction for which the value is 4?
I'll be completely honest, I don't even know where to begin on this question, I have never seen a problem like it before therefore I come to you guys lost and looking for help, anything will be appreciated.