What is the slope of the tangent line of (y/x)e^(x/y-x^2)= C (yx)exyx2=C, where C is an arbitrary constant, at (1,2)(1,2)?

1 Answer
Jun 2, 2018

10

Explanation:

Taking the logarithm of both sides gives us

ln y -ln x +x/y-x^2 = ln Clnylnx+xyx2=lnC

Differentiating with respect to xx yields

1/y dy/dx -1/x +1/y-x/y^2dy/dx-2x = 0 implies1ydydx1x+1yxy2dydx2x=0

(1/y-x/y^2)dy/dx =2x+1/x-1/y implies (1yxy2)dydx=2x+1x1y

x(y-x)dy/dx = (2x^2+1)y^2-xyx(yx)dydx=(2x2+1)y2xy

At the point (1,2)(1,2) we have

1 times (2-1)times dy/dx = (2 times1^2+1)times 2^2-1times 2 implies1×(21)×dydx=(2×12+1)×221×2
dy/dx = 10dydx=10

Hence the slope of the tangent at (1,2)(1,2) is 10

Note

I have assumed that tangent at (1,2)(1,2) means tangent to the curve at (1,2)(1,2). Of course, this means that the constant CC can not be arbitrary - but rather has to be 2/sqrt e2e