A voltage follower is the non-inverting feedback contract with direct output feedback. Exact arithmetic here means exact results for the stated model inputs; measured inputs still carry uncertainty and significant-figure limits.
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Direct feedback samples the output itself
The feedback path returns the output directly to the minus input.
V−=Vout
The follower copies the input within the rails
The input is 5 volts, so the output is also 5 volts.