Unfriendly Persuasion

 is a side quest in Fallout: New Vegas.

Quick walkthrough
Marcus asks you to convince some NCR mercenaries to go away peacefully. With a 65 speech check you can simply ask them to leave and complete the quest. If you are Idolized with the NCR you will have an dialogue option to use your NCR reputation to convince them to leave.

If you ask them how much it costs to bribe them they will say 2500 caps. You can get the caps from Marcus by asking him. Lie to him and you can get 3000 out of him. If you then use speech to convince them to leave, the player can keep the large amount of caps.

Detailed walkthrough
The second time the player returns after finding Jacobstown, Marcus will approach you with news of New California Republic mercenaries harassing the town. He'll then ask you to peacefully deal with them. When asked why the the mutants don't kill them Marcus says it's to avoid the NCR from having an excuse to terminate Jacobstown.

Finding the mercenaries is relatively easy, since they're directly in front of the town. To resolve the quest you can pay them 2500 caps or with a 65 Speech test, peacefully tell them to leave. If you have a very high NCR standing you may also be able to tell them that you're an NCR hero, and they'll leave without a speech check or paying them.

A way to get caps and loot but with NCR infamy is to go to Norton (mercenary leader), ask him how much it would cost for them to leave, then go back to Marcus and  to him for Bad Karma and get the 3,000 caps. Then get in a hidden position (behind them) and take every mercenary out with a silenced weapon, then go to Norton and either convince him to leave (65 Speech), or pay him 2,500 caps. Then head back to Marcus, and tell him you solved it "peacefully". You'll get their loot, (2x Plasma rifles, 2x Sniper rifles, Heavy armor, and associated ammo), and the least amount of caps you can receive is 500.

An alternate way of getting the caps and loot without gaining infamy is to complete the speech task, but then as Norton and the mercenaries are walking away, kill them one at a time while hidden. If the mercenaries bunch up too close to each other, talking to them will stop their walking momentarily.

1. Use a long range suppressed weapon and mines to take them out with sneak attack criticals and explosions (Or just a Silenced Sniper Rifle, head-shot sneak critical will kill them).

2. Take them out head on.
 * Note that there will always be 5 mercs (including Norton), all wearing metal armor/reinforced metal armor, combat armor and high-quality weaponry, so a head-on fight might prove difficult for some. Plus you'll lose A LOT of NCR reputation. This is not at all recommended (unless you're against the NCR of course, then it's highly recommended).

3. Attack them then run to Marcus (make sure he doesn't die, but he has 500HP and 15DT) and the other Super mutant and let them kill the mercenaries. (easiest)

4. Shoot them one after another (headshots or other one-hit-kills) from a position where only the person you're currently killing would be able to see you. It doesn't even have to be a silenced (or scoped, if your manual aim is good enough) weapon; the others will become hostile for a short while, then turn back to friendly/neutral.

5. Before you finish the last chat, fast travel away. Check back periodically. The local Cazadors will kill the mercenaries and you can just loot the bodies. If they kill Norton you can only get the aggressive ending, but if he lives to the last you can still get the peaceful one.

6. Prior to talking to Norton, use a silenced weapon to kill the four unnamed mercenaries for exp and their gear. Then, talk to Norton and resolve the issue peacefully however you wish. Do not kill Norton, doing so will close off certain dialog with Marcus. Let him walk away (you can also pickpocket him and get a little info on the reason for them attacking Jacobstown), then return to Marcus to claim your reward for 'peacefully' resolving the issue.

After completing the quest you will gain 350 XP.

Bugs

 * After convincing Norton to walk away via caps, the area just south of Silver Peak Mine shows a non-hostile NPC on the compass. The spot the compass points to shows an option to talk to Norton and one or more mercenaries. Doing so does not activate a dialog.
 * If Norton was killed by a Cazador, the only way to complete the quest is to kill the mercenaries.