Four is equal to five?

Question

Theorem: 4 = 5
Proof:
-20 = -20
16 - 36 = 25 - 45
4^2 - 9*4 = 5^2 - 9*5
4^2 - 9*4 + 81/4 = 5^2 - 9*5 + 81/4
(4 - 9/2)^2 = (5 - 9/2)^2
4 - 9/2 = 5 - 9/2
4 = 5

Answer 1

Clever! Liked it! But the next to the last line should have been:

±(4 - 9/2) = ±(5 - 9/2)

so that, for example,

+(4 - 9/2) = -(5 - 9/2)

which would be correct

Answer 2

This statement:
4 - 9/2 = 5 - 9/2

does not follow from
(4 - 9/2)^2 = (5 - 9/2)^2

learn some mathematics

|4 - 9/2| = |5 - 9/2|

Answer 3

from here:

(4 - 9/2)^2 = (5 - 9/2)^2

to here:

4 - 9/2 = 5 - 9/2

you cannot just take the square root straight away

because

a^2 = b^2

a = -b or b

if you evaluate 4 - 9/2 = -0.5 and 5 - 9/2 = 0.5

hence

(-0.5)^2 = 0.25 = 0.5^2

(4 - 9/2)^2 = (5 - 9/2)^2

BUT

4 - 9/2 =/= 5 - 9/2

Answer 4

hi dude!
4-9/2=1/2
5-9/2= -1/2
(4 - 9/2)^2 = (5 - 9/2)^2
but 4 - 9/2 = -(5 - 9/2)

Answer 5

You could have made it simpler by just starting at the step (-1/2)^2 = (1/2)^2 and therefore -1/2 = 1/2 ...

(Kids: This proof was done by a professional illogician, operating in an alternate reality. Do not try it yourselves at home or, most especially, in school ...)

Answer 6

well even u can prove that 1=2 in the same way but this proof is not valid

Answer 7

its so in genius that it is stupid

Answer 8

uhh, no.