How do they do that?

#1
I always thought I was pretty good at algebra, especially the simple stuff, but I saw this yesterday and I still can't figure out where the trick is:

(Where a2 is 'a' squared, b2 is 'b' squared and 2b is 2 times 'b'. I can't figure out superscript on here and pasting from word loses the formatting). The steps are numbered to make any potential answers easier to understand.

1. if a = b

2. a2 = ab

3. a2 -b2 = ab- b2

4. (a+b)(a-b) = b(a-b)

5. a+b = b

6. 2b = b

7. 2 = 1

What can't I see?
 
#2
(a+b)(a-b) = 0

b(a-b) = 0

a + b = 2b (or a + b =2a)

The break is between statement 4 and 5.

That's my go. Haven't done it since '73, though.
 
#4
To get from step 4 to step 5, you are dividing both sides by (a-b). As it is given that a=b, then a-b=0, this means you are dividing both sides by zero. There are lots of these look-crazy-at-first-glance equations around, but they all invariably involve dividing by zero, as that produces the required, odd, result!
 
#5
a and b cannot equal zero. Well, not unless you wish to argue zero equals zero, which seems a waste of time.
 
#6
This is just like walking into the Tech Workshops at NAAFI break, just without the darts!
 
#10
Agreed with what has been said and will add, zero will throw up daft solutions and also infinity will. I dont really count them as solutions though.

6. 2b=b this doesnt look right does it, two of something equalling one of something.
 
#11
I always thought I was pretty good at algebra, especially the simple stuff, but I saw this yesterday and I still can't figure out where the trick is:

(Where a2 is 'a' squared, b2 is 'b' squared and 2b is 2 times 'b'. I can't figure out superscript on here and pasting from word loses the formatting). The steps are numbered to make any potential answers easier to understand.

1. if a = b

2. a2 = ab

3. a2 -b2 = ab- b2

4. (a+b)(a-b) = b(a-b)

5. a+b = b

6. 2b = b

7. 2 = 1

What can't I see?
Equations 1-4 are generic, ie: apply for all values of a and b.
It starts to go wrong (the trick begins) at step 5, which is true only when a and b = 0 and NOT for all integer values of a and b.
Carrying on you get a divide by 0 from steps 6 to 7.
 
#13
Equations 1-4 are generic, ie: apply for all values of a and b.
It starts to go wrong (the trick begins) at step 5, which is true only when a and b = 0 and NOT for all integer values of a and b.
Carrying on you get a divide by 0 from steps 6 to 7.
Looking back at this now, it is irrelevant if a = 0 or any other value, because at step 3. both sides are equal to zero anyway. From there we are playing with either infinity or zero so all answers are true.
 
#14
Looking back at this now, it is irrelevant if a = 0 or any other value, because at step 3. both sides are equal to zero anyway. From there we are playing with either infinity or zero so all answers are true.
The value of A or B doesn't matter. If A = B then (A - B) = 0 and when you divide by 0 and accept the answer is a real number (which is what your equation is saying), then you can make any integer = any other integer.
 
#16
Soldier 1 has 20€, He wants to go out and get tanked at the Sqn bar. Becks is 1€ a bottle and a Kebab Compass is 3€. How many Becks can Soldier 1 smash down his fizzer before drunkenly following his Kebab Compass back to his pit?
Solution - 17
 
#17
Soldier 1 has 20€, He wants to go out and get tanked at the Sqn bar. Becks is 1€ a bottle and a Kebab Compass is 3€. How many Becks can Soldier 1 smash down his fizzer before drunkenly following his Kebab Compass back to his pit?
Solution - 17
This must be the consumerist version of the eternal truth that God looks after drunken soldiers and little children.
 
#19
The value of A or B doesn't matter. If A = B then (A - B) = 0 and when you divide by 0 and accept the answer is a real number (which is what your equation is saying), then you can make any integer = any other integer.
If a = what I said and b = what you said after that.

a=b

or a-b = 0

So what was your point?
 
#20
Soldier 1 has 20€, He wants to go out and get tanked at the Sqn bar. Becks is 1€ a bottle and a Kebab Compass is 3€. How many Becks can Soldier 1 smash down his fizzer before drunkenly following his Kebab Compass back to his pit?
Solution - 17
You Sir give Maths a bad name, unless you are trying us.
1: Minesweeper coefficient adds one becks free of charge for every pint swept
2: Desperate Munter buys you supper on the promise of filling your teeth with her clocksprings
3: Sell your combat jacket/entire 1157 for £30
4: Have a fight with your new det commander.


Pffft maths.
 

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