Idon’t understand the difference between number 3 and 4 , can somebody explain it to me pls?

36x2 + 49y2 = 1,764 the foci are located at: (-√13, 0) and (√13,0) (0, -√13) and (0,√13) (-1, 0) and (1, 0)edit: the answer is (- the square root of 13, 0) and (the square root of 13, 0)

If a company produces x units of an item at a cost of $35 apiece the function c=35x is a of the total production costs

Lana's family entered a 5-kilometer race lana's average step length is about 0.5 meter how many steps will she need to take the finish