Question

Which expressions are differences of squares?

Select each correct answer.



k2+81

p2−40

n2−225

t2−1

Answer 1

Answer: I took the test and here are the correct answers.

Explanation:

Answer 2

The correct options are 3 and 4.

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.