A non inverting op - amp amplifier is shown in figure. The o/p voltage is

Let the magnitude of the gain in the inverting op - amp amplifier circuit shown be $$x$$ with switch $${S_1}$$ open. When the switch $${S_1}$$ is closed, the magnitude of gain becomes.

The common mode voltage of a unity gain (voltage follower) op-amp buffer in terms of its output voltage $${V_0}$$ is __________.

Given figure, shows a non - inverting op - amp summer with $${V_1} = 2\,V$$ and $${V_2} = \, - 1V.$$ The output voltage $${V_0} = \_\_\_\_\_$$