How does this circuit even work?
I will make the following assumptions: pin 7 is the positive supply, and is connected to a positive supply V+ (but assumed, not shown), and pin 4 is connected to a negative supply V- (again, assumed but not shown.)

Then the two left-hand resistors provide a 1:1 divider to V+. To bring the - input to ground, current must balance, and $$\frac{V_{IN}}{R} + \frac{V+}{R} + \frac{V_{OUT}}{R} = 0$$ and since the R's drop out$$V_{OUT}= -(V_{OUT} + V+)$$