The amplitude is midway between the maximum and minimum values. The maximum is 6 and ther minimum is -3 (these are the y-values). That makes the amplitude (6- - 3) / 2 = 9/2 = 4.5
The period is the length of time (measured along the x-axis) for one full cycle. Notice that the function is at just over 1 (on the y-axis) when x = 0. It then drops to the minumum value and goes up to 2 (this looks like a V). Then the function continues increasing a little less sharply then more sharply before hitting the maximum value and heading back dwn. When x=5 the function is again at just over 1 and it repeats what I just explained. Since it took from x=0 to x=5 to see a full cycle (for the curve to do whatever it is before it started repeating) the period is 5.
Amplitude: 4.5
Period: 5