Discussion about math, puzzles, games and fun. Useful symbols: ÷ × ½ √ ∞ ≠ ≤ ≥ ≈ ⇒ ± ∈ Δ θ ∴ ∑ ∫ π -¹ ² ³ °

You are not logged in.

- Topics: Active | Unanswered

Pages: **1**

**Frublox****Member**- Registered: 2012-12-19
- Posts: 1

Got this problem on a test:

____

12 + √2x-1 = 4

Okay, so then I subtract 12 from both sides:

____

√2x-1 = -8

2x - 1 = 64 I then square both sides...

2x = 65 Add 1 to each side

x = 65/2 Divide both sides by two.

However, that answer doesn't work. Are there simply no solutions, then?

Offline

**bobbym****bumpkin**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 109,606

Hi Frublox;

That is correct, there are no solutions. Not every equation is a true statement. You always check the validity of your answer by plugging into the original equation.

Please go here:

**In mathematics, you don't understand things. You just get used to them.****If it ain't broke, fix it until it is.**** Always satisfy the Prime Directive of getting the right answer above all else.**

Offline

**bob bundy****Moderator**- Registered: 2010-06-20
- Posts: 7,972

hi Frublox

That answer is the solution to

-12 + √(2x-1) = -4

When you square you cannot help but introduce 'solutions' to this alternative equation as well so you were right to check the value you had.

Bob

Children are not defined by school ...........The Fonz

You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei

Offline

**anonimnystefy****Real Member**- From: Harlan's World
- Registered: 2011-05-23
- Posts: 16,037

Even when you got √2x-1 = -8 you could've said that there are no solutions, because a square root of a positive number is always positive...

Here lies the reader who will never open this book. He is forever dead.

Taking a new step, uttering a new word, is what people fear most. ― Fyodor Dostoyevsky, Crime and Punishment

The knowledge of some things as a function of age is a delta function.

Offline

**bobbym****bumpkin**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 109,606

Hi;

Yes, it always takes the principal value.

**In mathematics, you don't understand things. You just get used to them.****If it ain't broke, fix it until it is.**** Always satisfy the Prime Directive of getting the right answer above all else.**

Offline

Pages: **1**