Microeconomics: please help! MU&MRS?

Question

Find MU1, MU2 and MRS for the following utility functions:

(i) u(x1, x2) = 3x1 + x2

(ii) u(x1, x2) = 9x1 + 3x2

(iii) u(x1, x2) = ax1 + bx2

(iv) u(x1, x2) = x1ax2b

(v) u(x1, x2) = (x1 + a)(x2 +b)

(vi) u(x1, x2) = aln(x1) + bln(x2)

i'm not really understanding the MU and MRS stuff. please help??

Answer 1

take the partial derivatives for MU  MRS is ratio of MUs

i MU1= 3  MU2=1   MRS= - 3  becareful of what x you put on which axis here

ii MU1 = 9  MU2 = 3  MRS = -3

and so on