Star Delta Transformation

Which formula is correct for converting Y (Star) to Δ (Delta) in a resistive network?

Which formula is correct for converting $$\Delta$$ (Delta) to Y (Star) in a resistive network?

Three resistors (each is $$1\ \Omega$$ ) form a Y (star) circuit; Find the equivalent resistance between A and B.

Three resistors (each is $$1\Omega$$ ) form a $$\Delta$$ (delta) circuit; find the equivalent resistance between terminals A, B.

If the following circuit is transformed from Y (star) to $$\Delta$$ (delta), find the value of the resistance "R" ?

If the following circuit is transformed from $$\Delta$$ (delta) to Y (star), find "R" ?

Given a $$\Delta$$ network with resistances R1=9 Ω , R2=6 Ω , and R3=3 Ω , what is the value of the equivalent star resistor RA connected to the node between R1 and R2​?

What is the equivalent resistance between A, B?

What is the equivalent resistance between A, B?

What is the equivalent resistance between A, B?