Answer:
[tex]P(t)=4(1.019)^t[/tex]
Step-by-step explanation:
we know that
The equation of a exponential growth function is equal to
[tex]P=a(1+r)^t[/tex]
where
P ---> is the world's population
t ---> is the number of years since 1945
a ---> is the initial population in 1945
r ---> is the percent rate of growth
we have
[tex]r=1.9\%=1.9/100=0.019[/tex]
substitute
[tex]P=a(1+0.019)^t[/tex]
[tex]P=a(1.019)^t[/tex]
Remember that
There were approximately 4 billion people in the world in 1975
That means
Since year 1975 the initial value a=4 billion people
substitute
[tex]P(t)=4(1.019)^t[/tex]