Answer
a. since $t$ starts at $0$. Therefore, doesn't have the additive inverse of a positive integer as a domain.
b. $t(H)=\sqrt {\frac{100-H}{4.9}}$
c. $t(80)=2.02$ seconds
Work Step by Step
$H(t)=100-4.9t^2,$
a. since $t$ is time in second, $t$ starts at $0$. Therefore, doesn't have the additive inverse of a positive integer as a domain, the function is one-to-one. meanwhile, other quadratic function has a positive integer and additive inverse of those positive integer as a domain it will not be one-to-one.
b. $t(H)=\sqrt {\frac{100-H}{4.9}}$
c. $t(80)=\sqrt {\frac{100-80}{4.9}}=2.02$ seconds
