Answer:
x = 0, -4 and -3.
Step-by-step explanation:
The given expression is "3x to the power of 3 + 21x squared + 36x = 0".
We can write this expression as follows :

Taking 3x common.

x = 3

Hence, the solution of the given quadratic equation are x = 0, -4 and -3.
Answer:
0 People initially had the cold.
6 People will have it after 2 days.
Step-by-step explanation:
To find out how many people had it initially, plug 0 in for x (implying 0 days later.)
C= 1*3(0)
C= 1*0
C=0
Nobody had the cold initially.
To find out how many people had it after 2 days, plug 2 in for x. (implying 2 days later.)
C= 1*3(2)
C= 1*6
C=6
Therefore 6 people had the cold after 2 days.
I hope this helps!