Use the Gradient to Find the Directional Derivative of the Function

question 16

Multiple Choice

Use the gradient to find the directional derivative of the function at P in the direction of Q. $$g ( x , y ) = x ^ { 2 } + y ^ { 2 } + 1 , \quad P ( 4,8 ) , \quad Q ( 12,24 )$$

• A) \(- 4 \sqrt { 5 }\)
• B) \(8 \sqrt { 5 }\)
• C) \(16 \sqrt { 5 }\)
• D) \(4 \sqrt { 5 }\)
• E) \(- 8 \sqrt { 5 }\)