How do I solve it? Please explain it for me

1. [-/7.69 Points] DETAILS Calculate fx(x,y), fy(x,y), fx(1, -1), and fy(1, -1) when defined. (If an answer is undefined, enter UNDEFINED.) f( x, y) = 500 + 3x - 4y fx ( x, y) = f ( x , y ) = fx(1, -1) =[ fy(1, -1) =[ 2. [-/7.69 Points] DETAILS WANEFMAC7 15.2.003. Calculate - of of of ax' ay ax (1, -1)' and of ay ( 1, -1) when defined. (If an answer is undefined, enter UNDEFINED.) f (x, y) = 4x2 - y3 + x - 7 of ax of ay of ax (1, -1) of ay (1, -1) 3. [-/7.69 Points] DETAILS WANEFMAC7 15.2.005. Calculate of of af ax ay ax (1, -1)' and of ay (1, -1) when defined. (If an answer is undefined, enter UNDEFINED.) f(x, y) = 7,000 - 55x + 10y +15xy of ax of ay of ax (1, -1) of ay (1, -1) 4. [-/7.69 Points] DETAILS Calculate fx(x,y), fy(x,y), fx(1,-1), and fy(1,-1) when defined. (If an answer is undefined, enter UNDEFINED.) f ( x, y ) = 8x2y fx ( x, y ) = fy ( x, y ) = fx(1,-1) = fy (1, -1) = 5. [-/7.69 Points] DETAILS WANEFMAC7 15.2.010. Calculate of of of ax ay ax (1, -1)' and of ay (1, -1 ) when defined. (If an answer is undefined, enter UNDEFINED.) f( x, y ) = x -5y2 + xy2 + xy of ax of av of ax (1, -1) of ay (1, -1) 6. [-/7.69 Points] DETAILS WANEFMAC7 15.2.011.MI. Calculate of of af ax ay ax (1, -1)' and of ay (1, -1) when defined. (If an answer is undefined, enter UNDEFINED.) f ( x, y) = (2xy + 1)3 of ax of av of ax (1, -1) of ay (1, -1)