Last two steps incorrect.
It's m² < 16, not m² > 16.

is it like this
m² < 16
m > ± 4
Hence -4< m < 4.

There's no such thing as m > ± 4

If m is already bigger than 4 , there's no need to write it's bigger than -4 because it's alr understood



m² < 16

Notice that m² can be = -m x -m or
m x m

You know 4 x 4 = 16
- 4 x - 4 = 16

So if m² is smaller than 16, then
m has to be smaller than 4 or m is bigger than -4.

(Eg. Let's say m = 3 whereby 3 < 4.
3 x 3 = 9 < 16.
If m = -3, whereby -3 > -4,
-3 x -3 = 9 < 16)

So -4 < m < 4.

The correct way to present this is :

m² - 16 < 0

(m + 4)(m - 4) < 0


-4 < m < 4

I see. ......... thank you