Tasks: Let's continue taking partial derivatives. Go to Example 11.3 and work through yourself how the three derivatives (with respect to 𝑥 , 𝑦 , and 𝑧 ) were computed. At the end of Example 11.3 we are also introduced to the definition of the gradient of a function. If 𝑓 is a function of 𝑛 variables and all the partial derivatives exist, then the gradient of 𝑓 is defined to be ∇ 𝑓 ( 𝑥 ) = ( ∂ 𝑓 ∂ 𝑥 1 ( 𝑥 ) , ∂ 𝑓 ∂ 𝑥 2 ( 𝑥 ) , … , ∂ 𝑓 ∂ 𝑥 𝑛 ( 𝑥 ) ) . This video goes over the definition and some facts on notation: Question: Which of the following functions have gradient ∇ 𝑓 = ( 𝑦 𝑒 𝑥 𝑦 + 𝑦 , 𝑥 𝑒 𝑥 𝑦 + 𝑥 ) ?单项选择题