Answer: First you'll want to determine just why the grass is dried out. Maybe the sprinkler isn't reaching the area; perhaps the areas are a result of dog urine; the grass may be diseased in the dry areas. Whatever the cause, you'll want to correct it so that any new grass you put in the area will have a fighting chance.
Once you've determined the cause, you can rake out the dead grass and roots and then reseed. Cover the grass seeds with some peat moss to help keep the seeds from drying out and then water (several times a day if necessary) to keep the grass seeds moist. They should sprout in 7-10 days. Keep the lawn well watered and the bare spots should fill in within a few weeks.
Best wishes with your lawn!
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