Quick question: x^2-y^2=16 (find x)

1. Feb 22, 2017

sobergeek23

1. The problem statement, all variables and given/known data
x^2-y^2=16
isolate the variable x

2. Relevant equations
square roots

3. The attempt at a solution
x^2=y^2+16

x=y+4?

2. Feb 22, 2017

BvU

Because your $x^2 = (y+4)^2 \ne y^2+16$

3. Feb 22, 2017

sobergeek23

4. Feb 22, 2017

sobergeek23

if i squared both sides it would just be the individual answer

5. Feb 22, 2017

BvU

What's the full problem statement ? 'Isolate' doesn't sound like a question with an answer ...

6. Feb 22, 2017

sobergeek23

that was the problem..it just said isolate the variable x..

7. Feb 22, 2017

Mastermind01

NO! This is a fundamental mistake. $\sqrt{a+b} \neq \sqrt{a} +\sqrt{b}$

8. Feb 22, 2017

Mastermind01

Isolate probably means solve for x in terms of y.

9. Feb 22, 2017

sobergeek23

said something like it is understood to be positive or something like that

10. Feb 22, 2017

sobergeek23

we were solving equations where you square both sides

11. Feb 22, 2017

BvU

In that case you are done when you write $x^2 = y^2 + 16$ : it has x in isolation on the left hand side of the $=$ sign.

12. Feb 22, 2017

sobergeek23

it cant be a square

13. Feb 22, 2017

Mastermind01

• Poster has been reminded (too late) not to post answers to schoolwork questions on the PF
So the answer is just $x = \sqrt{y^2 + 16}$ NOT $y+4$

14. Feb 22, 2017

BvU

Rapid fire of posts from three sides ...

Ok, semantics: isolate means write it so that it says $x =$

What do you have to keep in mind when going from $x^2 = ...$ to $x = ...$ ?

15. Feb 22, 2017

sobergeek23

why doesnt that reduce?

16. Feb 22, 2017

BvU

Watch out MM ! PF hates direct answers. it ruins the learning experience

17. Feb 22, 2017

sobergeek23

learning experience means frustration and anger and deletion of account for me...

18. Feb 22, 2017

Mastermind01

Let's keep it cool. What's $(a+b)^2$?

19. Feb 22, 2017

sobergeek23

a^2+b^2

20. Feb 22, 2017

BvU

It does reduce, but you have to be careful...
I recognise the frustration and anger. Don't get carried away, sit back and think a bit now and then before firing of another post and the 'deletion of account' may be replaced by 'satisfaction from deeper udnerstanding'