If ∑anxn\sum a_n x^n∑anxn has radius R1R_1R1 and ∑bnxn\sum b_n x^n∑bnxn has radius R2R_2R2, what is the radius of convergence of ∑anbnxn\sum a_n b_n x^n∑anbnxn?
R1+R2R_1 + R_2R1+R2
min(R1,R2)\min(R_1, R_2)min(R1,R2)
R1R2R_1 R_2R1R2
max(R1,R2)\max(R_1, R_2)max(R1,R2)