In the op-amp circuit V0 is given by:

Due to virtual ground voltage at terminal A is V_s KCL at node A.

	V_s	+	V_s – V_o	= 0
	R		2R

	V_s	+	V_s	=	V_o
	R		2R		2R

V_s		3R		=	V_o
		2R²			2R

or V₀ = 3 V_s
Alternative method

V₀ = V_s		1 +	2R		= 3 V_s
			R