$A$ function $f$ is defined by $f(x) = 2x - 5$. Find the value of $f(-3)$.

Examine the following relation and state whether it is a function or not,giving reasons:
$R = \{(1, 2), (2, 3), (3, 4), (4, 5), (5, 6), (6, 7)\}$

Which of the following is $NOT$ a function?

Examine the following relation and state whether it is a function or not,giving reasons:
$R = \{(2, 1), (3, 1), (4, 2)\}$

Let $N$ be the set of natural numbers. Define a function $f: N \rightarrow N$ by $f(x) = 2x + 1$. Using this definition,complete the table given below.

$x$	$1$	$2$	$3$	$4$	$5$	$6$	$7$
$y$	$f(1) = \dots$	$f(2) = \dots$	$f(3) = \dots$	$f(4) = \dots$	$f(5) = \dots$	$f(6) = \dots$	$f(7) = \dots$

If $f$ is a relation from the set of positive real numbers to the set of positive real numbers defined by $f(x) = 3x^2 - 2$,then $f$ is