Aaaaaa..
Weka minofu tuione mzee wa maths...😀
P=population at time t
c=initial population
k=rate of growth
dP/dt=kp...
dP=kpdt...
dP/p=kdt...
Integrate both sides
∫dP/p=∫kdt
In(P)=kt+c
take out (In)
P'=e^kt+c
P=e^c+e^kt
e^c=c
P=c.e^kt..............general formula of expontential growth/and or decay...
Doubling time...
P=2c
with P=c.e^kt
2c=c.e^kt
cancelling c..
2=e^kt.........doubling time formula
Lugha kawaida inawachanganya sana wanafunzi wengi bongo japo wanajua sana hesabu...
wanatakiwa kujua kubalisha statement kuwa hesabu na hapo ndio ugumu....
Lakini ukiwaletea za 4x^3+2x^2+3x+5=0.......wanazipopoa hasa....
For the case of the Qns, let me put mnofu.
Starting from; lnP=kt+C ----(1)
At t=0, P=1000, plugging into eqn 1
➡ln1000=0×k+C, therefore, c=ln1000,
Plugging c=ln1000 into eqn 1 to have a specific eqn,
➡lnp=kt+ln1000 -----(2)
The given condition is; for 30 years the population doubles, that is starting t=0 after t=30 years the population will be 1000×2=2000 humans, plugging the stuffs into eqn 2, finding k,
➡In2000= 30k+ln1000, rearranging for k;
In2000-ln1000=30k
ln(2000/1000)=30k
Therefore k=(ln2)/30
Now the eqn2 becomes;
ln p=(ln2)/30t+ln 1000
lnp=ln2^0.033333t +ln1000,
lnp=ln(2^0.03333t×1000), removing ln frim both sides of the equation
➡P=2^0.033333t×1000, that is the equation to be used to solve the Qns:
1----The population p after 40 years.
2----The time t for the population to become tenfold.