I have a similar problem as javier acha already described here Convert from a specifc range to another one which is to map a (AC, 100Hz) voltage range from [-12V, +12V] to [0V, 4V]. I am currently trying to solve it using the OpAmp approach.
This is why I have (a very basic) question concerning Spehro Pefhanys suggested circuit (see link):
What do I actually need R6 and R7 for? Can I also just leave them away?