The number of users on a new social media platform was tracked over several years.
Exactly 4 years after tracking began, the number of users was 42 000.
Exactly 8 years after tracking began, the number of users was 56 000.
Given that the number of users, U U\,U thousand, t t\,t years after tracking began can be modelled by the equation
U2=a+bt2 U^2 = a + bt^2 U2=a+bt2where a a\,a and b b\,b are constants,
find the value of a a\,a and the value of bbb.
According to the model, exactly T T\,T years after tracking began, the number of users was 75 000.
Making your method clear,
find the value of TTT, giving your answer to one decimal place.
(Solutions relying entirely on calculator technology are not acceptable.)
