Question

2+2=5
proof
My teacher said we must prove 2+2=5 there is a way and he wants us to find out.

Answer 1

x = y
x^2 = xy
x^2-y^2 = xy-y^2
(x+y)(x-y) = y(x-y)
x+y = y
2y = y
2 = 1
1 = 0

Now since 2+2 = 2+2+0 and we apply the lemma proof so that 0 = 1, 2+2+0 = 2+2+1 =5

THEREFORE
2+2 = 5

Answer 2

That is called the Robin Lemma proof, I believe.

Answer 3

@Futuristicmario

Answer 4

There is not a way that is without error, but it shouldn't be too hard. 0 = 1 is pretty common. Adding 4 to that might easily produce 4 = 5.

The usual might be:

1) Start with two unequal numbers, a and b
2) c = (a+b)/2 - the average of a and b
3) The 2c = a+b
4) Since a-b is not zero 2c(a-b) = (a+b)(a-b) ==> 2ac - 2bc = a^2 - b^2
5) Algebra: a^2 - 2ac = b^2 - 2bc
6) Add c^2: a^2 - 2ac + c^2 = b^2 - 2bc + c^2
7) Factor: (a-c)^2 = (b-c)^2
8) Square Root: a-c = b-c
9) Add c: a = b
10) Take a = 5 and b = 4, which are NOT equal, for 1), and we have from 9) 5 = 4 = 2+2.

Wasn't that fun!?

Please Note: There ARE errors in there.

Answer 5

@calculusxy :???
(x+y)(x-y) = y(x-y) ????
(x+y)(x-y)=x^2-y^2
I think !:)

Answer 6

for large values of two, eg 2.3

2.3+2.3 =4.6 = 5 , a small value for five