Answer:
f(x) = x(x-1)
Step-by-step explanation:
The easy way to do this is to look at it graphically. an inverse function is reflected across the line y=x. f(x)=x(x-1) is an upward opening parabola when reflected, there are two y-values for all positive values of x. A function can only have one y for every x.
I believe that the answer may be 1,1,1,2
R = speed in still water
r + c = speed with current
r - c = speed against current
3.5(r + c) = 70
r + c = 20
c = 20 - r
4(r + c) = distance from pier to pier
5(r - c) = distance from pier to pier
4(r + c) = 5(r - c)
4(r + 20 - r) = 5(r - 20 + r)
80 = 10r - 100
180 = 10r
18 = r
The speed in still water is 18 km/hour
