Indifference curve?

Question

so i know that the slope of the indifference curve is the MRS and i know what the equation for MRS is. but how do i find the slope (aka the MRS) for this equation: xA = 100/xB and the slope (MRS) for this equation: xA = 120/xB?

i'm not supposed to evaluate it, just give the equation. but i don't know what that means and i don't know how to do this.

PLEASE HELP!! something to do with partial deriv? i don't get it

Answer 1

xA = 100/xB

100xA = xB

xA/xB = 100 -

that's your MRS - 100 A for 1 B.

Answer 2

I'm guessing (tell me if I'm wrong) that 100 and 120 are the levels of utility.  So the utility function would be U=(xA)(xB)

Remember the MRS equation, MRS=U1/U2, where U1 is the derivative of the utility function in terms of xA and U2 is the derivative in terms of xB.

So, U1=dU/d(xA)=xB*1=xB

And U2=dU/d(xB)=1*xA=xA

So MRS=xB/xA

Did that help?