Given that x+y=3 and x^2-y^2=24, find the value of 2x -2y

[Oskar]

Given that x+y=3 and x^2-y^2=24, find the value of 2x -2y
I have no clue how to do it

 

[Otis]

Given that x+y=3 and x^2-y^2=24, find the value of 2x -2y
I have no clue how to do it

Hi Oskar:

Here are some clues.

Factor the expression 2x-2y. Then note that, if you knew x-y, you could just double it.

Next, the expression x^2-y^2 is called a difference of squares. Use the special factoring-pattern (for a difference of squares) to factor the expression x^2-y^2.

After you have factored the difference of squares, rewrite the given equation. You can also substitute the given value for the expression (x+y), and go from there.

If you need more help to finish, please show us what you have done so far.

Cheers

 

[stapel]

Given that x+y=3 and x^2-y^2=24, find the value of 2x -2y
I have no clue how to do it

When you "have no clue how to do it", you can always try stuff. You know that x^2 - y^2 = (x + y)(x - y). You know that you've been given a value for x^2 - y^2 and for x + y. And then you can look at what they've asked you about, and notice how it relates, being twice the other factor of x^2 - y^2. Where does this lead?