Original sentence: That is, using resistors alone it is not possible to either invert the voltage or increase Vout above Vin
Edited sentence: For this purpose, the voltage divider is connected in the loop of either parallel or series negative feedback thus obtaining either an "inverting voltage divider" with ratio -R2/R1 (op-amp inverting amplifier) or a "reversed voltage divider" with ratio 1 + R1/R2 (op-amp non-inverting amplifier).That is, using resistors alone it is not possible to either invert the voltage or increase Vout above Vin since this would involve the creation of energy; this is possible only if the required energy is supplied from an external source such as a properly supplied op-amp