Suppose
f
is a linear function and
f
(
x
)
varies at a constant rate of change of 1.5 with respect to
x
. Suppose we know that
f
(
1.3
)
=
2.1
.

Suppose
x
varies from
x
=
1.3
to
x
=
1.5
...

How much did
x
change by?