Madeline was completing the square, and her work is shown below. identify the line where she made her mistake.
f(x) = 3x2 + 6x − 7
line 1: f(x) = 3(x2 + 2x) − 7
line 2: f(x) = 3(x2 + 2x + 1) − 7 − 1
line 3: f(x) = 3(x + 1)2 − 8

Marcus and cody both leave the park at the same time, but in opposite directions. if cody travels 6 mph faster than marcus and after 4 hours they are 64 miles apart, how fast is each traveling? solve using rare times time = distance.