Answer:
Maximum rate of change at the point (-1,2) = √17
Direction is the direction of the gradient
Step-by-step explanation:
The gradient of a function (scalar or vectorial ) is a vector in the direction of maximum rate of change then
f( x,y ) = x*2y + 2y
grad = δ/δx i + δ/δy j + δ/δz k
grad f(x,y) = [ δ/δx i , δ/δy] = [ 2y , x+2 ]
at the point ( -1 , 2 )
grad f(x,y) = [4 , 1]
| grad f(x,y) | = √ (4)² + (1)² = √17
