Question:
Let $f=\{(0,-5),(1,-2),(3,4),(4,7)\}$ be a linear function from $Z$ into $Z$.
Write an expression for f.
Solution:
Given that: $f=\{(0,-5),(1,-2),(3,4),(4,7)\}$ be a function from $Z$ to $Z$ defined
by linear function.
We know that, linear functions are of the form y = mx + b
Let f(x) = ax + b, for some integers a, b
Here, $(0,-5) \in f$
$\Rightarrow \mathrm{f}(0)=-5$
$\Rightarrow \mathrm{a}(0)+\mathrm{b}=-5$
$\Rightarrow \mathrm{b}=-5 \ldots(\mathrm{i})$
Similarly, $(1,-2) \in f$
$\Rightarrow f(1)=-2$
$\Rightarrow a(1)+b=-2$
$\Rightarrow a+b=-2$
$\Rightarrow a+(-5)=-2[$ from (i) $]$
$\Rightarrow a=-2+5$
$\Rightarrow a=3$
$\therefore f(x)=a x+b$
$=3 x+(-5)$
$f(x)=3 x-5$