[Greybeard]

You didn't say how wide the cracks are, but if they are typical 1/4 to 3/8, here's a quick repair method: Don't V them out - no need. Run masking tape over the crack end to end. Take a sharp utility knife and cut the tape along the edges of the crack, so only the crack is exposed. Caulk the crack full to the top. I'd recommend either polyurethane, which stretches the most, or a silicone that is designed for concrete. While the caulking is still wet, either cover it with sand, or if you really want a neat job, take a wire brush in a drill and buzz the concrete next to the crack so the dust covers the wet caulk. Next day pull the tape and blow off the excess sand or concrete dust. The repair will be a lot less noticeable with the dust or sand embedded in the caulk. Good luck.

 

[Greybeard]

Sikaflex 1A as shown in the photo is a good choice. That's because it IS a polyurethane (I've got a tube right here). Also, it's NOT self-levelling, because the application in the photo is vertical, and self-levelling materials are for horizontal applications. They level themselves out before they cure. And they would slump out of the vertical joint in the photo. You can check this on their website. There are many brands with equal properties, made by Tremco, Pecora, GE and even DAP, among others.
If the cracks are deep, fill them almost full of sand or use a joint backer rod before you caulk. You don't want a deep application, because a thick strip of caulking is like a thick piece of rubber - it will break rather than stretch. Ideal shape is a joint width twice the depth - like 1" wide by 1/2" deep.