This is the concept of differential equations, given that
dp/dt=rp
then:
dp/p=rdt
thus:
ln p=rt+C
p=e^(rt+C)
P=Ke^(rt)
when t=210 days=7 months, p=2k
2k=k×e^(7r)
2=e^(7r)
ln2=7r
r=ln(2)/7
r=0.0990
Since y=2x+1 does not pass through the origin (i.e. there exists the constant term of 1 ), the variables y and x are not directly proportional - though, they do have a linear relationship.
You normally use pie in equation that had the circumference or radius or diameter. !<span />
