If you feel like you have a decent or average amount of gold compared to everyone else and you have spent it in ideally optimized items, then hypothetically the way you would 1v5 is you try to land your stun on all their carries, delete the APC, delete the ADC, delete the jungler, delete the top, and then delete the support as an afterthought.
Also Jax top is boring. Play him in the jungle. AD Marks, Armor/lvl Seals, Flat AP Glyphs and Quints. For masteries, go 21/9/0. Ignore the executioner line. Put those points into the AP line. Get Stalker's Blade, or Poacher's Blade, or Ranger's Blade. Get the Magus enchantment. Rack up a kill or two by deleting people with surprising damage during your ganks. Build a BotRK, maybe rack up another kill or two. You now have a lead. Maintain it by building tanky via a Banshee's Veil and/or a Randuin's Omen. Build a Triforce if they have no damage, build a Iceborn Gauntlet if they have AD damage, build a Maw of Malmortius if they have AP damage. Finally, sell your boots to get Zephyr.
You're still essentially the team's tank, unless your team has a better one or unless your teammates aren't complete idiots and know how to read the map and avoid teamfights and keep fighting small skirmishes. In theory, Jax is a motherfucking assassin and he should never go in first. But in practice, because your teammates are all complete idiots, you build a lead early and then go tanky to maintain it and because your dumb fucking teammates will expect you to be the first one in. Now, if you want to go fullblown assassin Jax you can...
Anyway for spells you go Smite and Teleport.
