What type of number is -6.9

Imagine a new pasture with grass growing on it. every day after the seeds have germinated, the number of blades of grass in the pasture triples. after 18 days, the entire pasture is completely covered in grass. how many days did it take for the pasture to be one-third covered in grass?

In which figure is de bc ? a. figure 1 b. figure 2 c. figure 3 d. figure 4

Which shows the correct substitution of the values a,b and c from the equation 1=-2x+3x^2+1