Question

Multiply (x + 3)(x – 3).

A. x2 + 6x + 9
B. x2 – 9
C. x2 + 6x – 9
D. x2 – 6x + 9

I can't focus.

Answer 1

B would be correct the -3 x and 3 x cancel out

Answer 2

The answer is B.
`x^2-9`

Explanation:

This problem represents a "the Sum and Difference of the same two terms".

If you encounter the same two terms and just the sign between them changes, rest assured that the result is the square of those two terms. Also, the second term will always be negative.

For example:

`(a-b)*(a+b)=a^2-b^2`

So, in this case:

`(x+3)*(x-3)\\x^2-3*x+3*x-9\\x^2-9`

Therefore, the answer is B.
`x^2-9`