Final answer:
The initial value refers to the height of the flower at t=0 weeks, which is 4 mm, and the growth rate is how much the flower height increases every week, which is 2.1 mm/week.
Step-by-step explanation:
The height of the young flower is described by a linear equation H = 2.1t + 4, where H is the height in millimeters and t is the time in weeks since the first of this month. The equation is in the slope-intercept form, which is y = mx + b, where m is the slope (rate of change), and b is the y-intercept (initial value when x=0). Therefore, the initial value is 4 mm (the height of the flower at t=0 weeks), and the growth rate is 2.1 mm/week (the amount the flower's height increases each week).