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Part $1$

Let h be the function defined by

h left parenthesis x right parenthesis equals x squared minus $4,$

where the domain is the set of real numbers.

$($a$)$ Find

$$h$(1).$

$($b$)$ Find

$$h$($negative $1).$

$($c$)$ If

h left parenthesis t right parenthesisequals$12,$

what are the possible values of$$ t$?$

$($d$)$ Find

$$h$(6\mathrm{.}89).$