These are normally 560R. One goes from D- (pin 7 on 75176) to 0volts and another from D+ (pin 6 on 75176) to 5volts. These resistors bias the 485 bus to idle so the 75176 will output a '1' to the rxd pin on the micro. Only one device on the 485 bus should have this. If you use a MAX485 instead of the 75176 will will avoid this issue but nevertheless it is good practice to include the bias resistors along with 120R termination resistors
These values will lead to an incorrect termination impedance.
The correct values are 750 ohms for bias and 130 ohms for temination when biased.
It does not matter if you bias both ends or one end only, but you must terminate both.
refer to 10 ways to bulletproof 485 in the beset serial.. found in links <---.

Erik