Maths Question for Bilthehut and any other loser

[Mince]

I am thinking of a number. If I subtract five from this number and then multiply the result by itself, I get 9. What is the number I am thinking of?

There are two answers to this question.

[Tarquin Thunderthighs lll]

One answer is 8, and I get to be a loser.

The other answer is "**** off - I'm no loser!"

[Mince]

Yes, one answer is 8. Tell me the other answer and I'll officially and without reservation announce to the whole forum that you are less of a loser.

[Bilthehut]

Boring.  -2.

[Tarquin Thunderthighs lll]

Wrong! 

[Mince]

Tarquin's right. You're wrong, Bilthehut.

Go on then, Tarquin. Tell us the other one. No one else has a hope in hell.

[Tarquin Thunderthighs lll]

Ah, but I don't think you know either. Tell us what you think it is, and tell you if you're right.

[Bilthehut]

Boring.  -2.

Whoops!   Too much negativity in the air.  The answer should have been 2.

[Tarquin Thunderthighs lll]

Oh, great - now we'll never know if Mincey knew the answer. 

[Mince]

I'd like to see Bilthehut show how to get both answers using algebra.

[Tom]

I am thinking of a number. If I subtract five from this number and then multiply the result by itself, I get 9. What is the number I am thinking of?
There are two answers to this question.

Should that be I am thinking of two numbers, then?

[Tarquin Thunderthighs lll]

I'd like to see Bilthehut show how to get both answers using algebra.

I doubt if he even wears one.

[Bilthehut]

Is it a green one?

[Bilthehut]

The question can be shown as:

I am thinking of a number "x". If I subtract five from this number "x-5" and then multiply the result by itself "(x-5) times (x-5) is (x-5)²", I get 9 "(x-5)²=9". What is the number I am thinking of?

There are two answers to this question.

This is therefore (x-5)²=9
then (x-5)(x-5)=9
Multiplying this, we get x² - 5x - 5x + 25 = 9
Simplifying, this becomes x² - 10x + 16 = 0
Which then is (x-2)(x-8)=0
Meaning x is either +2 or +8

So there, Mincy-poo 
 

[Mince]

I love how you multiply it out and then factorise it again.

Here is the easy way.

(x - 5)² = 9

Square root both sides.

x - 5 = 3 or -3

Add 5 to both sides.

x = 8 or 2