Hello everyone, i have 2 problems in my multivariable calculus homework that i can't solve . Please help me out, thank you so much(adsbygoogle = window.adsbygoogle || []).push({});

1/f(x,y)= [(x^2) -2y]^(0.5)

a) Find directional derivatives of f at (2,-6) in the direction of <-4,3>

b) Find equation of the tangent plane to the function f(x,y) in problem 1 at the point (2,-6)

i got the part a) and but i have no idea how to do part b)

2/

a)Use Lagrange multipliers to find max and min of function P(x,y) = x(y^2) +(x^3)y-5xy subject to the constraint boundaries xy = 4 , y = x+3 , y = x-3

b) find absolute maximum and minimum on the region bounded by xy <= 4, x-3 <= y <= x+3 .

i spent an hour for this problem but couldn't solve for it

**Physics Forums | Science Articles, Homework Help, Discussion**

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Need help with Lagrange multipliers

**Physics Forums | Science Articles, Homework Help, Discussion**