Originally Posted by

**FrustratedCollegeKid** I have to find the slope of the tangent line to the curve at the point (2, 8):

√4x+4y + √2xy = 12

Or also can be written as:

(4x+4y)^(1/2) + (2xy)^(1/2) = 12

I tried differentating got got:

(d/dx)[(4x+4y)^(1/2)] = (1/2)*(4x+4y)^(-1/2)*[4+4(dy/dx)]

(d/dx)[(2xy)^(1/2)] = (1/2)*(2xy)^(-1/2)*[2y+2x*(dy/dx)]

then,

(2+2*(dy/dx))/(4x+4y)^1/2 + (4+x*dy/dx)/(2xy)^(1/2)

I then plugged in numbers and ended up with (4+4sqrt5)/((-2sqrt5)-4). However that answer is wrong. Can anyone give a clue as to what i did wrong?