Finding the thevenin resistance

Question

The task is to find the thevenin equivalent (seen form terminals a and b) of the following circuit:

I believe I have found the thevenin voltage by simply finding the voltage drop over the 5 ohm resistor, which is in parallel with the 5A current source (if there is a better way to approach this please let me know). However, finding the thevenin resistance of this circuit puzzles me. I am aware of the method of short circuiting and open circuiting independent voltage and current sources. I apply this which reduces to the following:

However as we are looking for the thevenin resistance from terminals a and b, I am confused with how to deal with the 5 ohm connected to the node connecting the 10 and 8 ohm resistors. Is it connected in paralled with the 8 ohm resistor, or do we ignore it? Any help will be deeply appreciated. Thanks in advance.

Answer 1

Since there is no current through the 5 ohm resistance (the one at the right), you can consider that the 10 ohm and 8 ohm resistances are connected in series (two resistors are connected in series if the same current passes through them). Thus, the Thevenin resistance is (10+8) // 5 = 3.9 ohm.