Is {4, ...} a defined set?

Ineed with number 6 , explain how to get 1978

Find the center and the radius of the circle with the equation: x^2-2x+y^2+4y+1=0?

Julie goes to the sports store and spends $40.50 before tax. she buys a pair of shorts for $21.75 and 3 pairs of socks that each cost the same amount. how much does each pair of socks cost? $$