Select all relations that represent a function. {(–5, 4),(–4, 3),(–3, 2),(–2, 1)} {(3, 11),(–4, 5),(3, –1),(0, 0)} {(5, 7),(2, 7),(9, 7),(8, 0)} {(0, 0),(–1, 3),(–1, –1),(0, 5)} {(8, 0),(1, 4),(9, 4),(7, 8)} {(–4, 3),(–2, 4),(0, 1),(–4, –1)}

Aboat has a speed of 9 mph in calm water. it takes the boat 4 hours to travel upstream but only 2 hours to travel the same distance downstream. which equation can be used to find c, the speed of the current? 2(9 – c) = 4(9 + c) 9 + c = 4(9 – c) 9 – c = 2(9 + c) 4(9 – c) = 2(9 + c)