The best way to solve this problem is to graph all variables, velocity being the dependent variable (y-axis) and time being the independent variable (x-axis) . Since we are given two points for the two variables, we use the point-slope formula to get the slope which happens to be -1. We then use the standard form y = mx + b and substitute m with -1. Next we want to find b, we will again use the point slope formula now knowing m to be -1. we chose point 0 for time(x-axis) and at zero, we obtain a value of your b which happens to be +19. A line graph would better visualize my point. Cheers!
Bryan is observing the velocity of a cyclist at different times. After four hours, the velocity of the cyclist is 15 km/h. After seven hours, the velocity of the cyclist is 12 km/h. Part A: Write an equation in two variables in the standard form that can be used to describe the velocity of the cyclist at different times. Show your work and define the variables used. (5 points) Part B: How can you graph the equations obtained in Part A for the first 12 hours? (5 points) PLEASE HELP!! its due tonight!