The Depth of a Pond at the Point with Coordinates $h ( x , y ) = 5 x ^ { 2 } + 4 y ^ { 2 }$

question 29

Essay

The depth of a pond at the point with coordinates (x, y)is given by $h ( x , y ) = 5 x ^ { 2 } + 4 y ^ { 2 }$ .(Assume that x, y, and h are measured in feet.)If a boat at the point (-3, -5)is sailing in the direction of the vector $5 \vec { i } + \vec { j }$ ,
then at what rate is the depth changing?

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