Question

Which expressions are differences of squares?

Answer 1

   
$\text{Differences squares are:}\\\\ n^2 - 255 = \boxed{n^2 - 15^2 } \\ \\ t^2 - 1 = \boxed{{t^2 - 1^2}}$

Answer 2

Answer:

The correct options are 3 and 4.

Step-by-step explanation:

The difference of squares is defined as

$a^2-b^2$

In option 1,

$k^2+81$

It can be written as

$k^2+9^2$

It is the sum of squares, therefore the option 1 is incorrect.

In option 2,

$P^2-40$

The number 40 is not a complete square of any number, therefore option 2 is incorrect.

In option 3,

$n^2-225$

It can be rewritten as

$n^2-(15)^2$

It is the difference of squares, therefore option 3 is correct.

In option 4,

$t^2-1$

It can be rewritten as

$t^2-1^2$

It is the difference of squares, therefore option 4 is correct.