And you thought you knew math...
Statement: 4 = 5
Proof
(1) -20 = -20
(2) 16 - 36 = 25 - 45
(3) 42 - 36 = 52 - 45
(4) 42 - 36 + (9/2)2 = 52 - 45 + (9/2)2
(5) (4 - 9/2)2 = (5 - 9/2)2
(6) 4 - 9/2 = 5 - 9/2
(7) 4 = 5.
SPOILER: Don't read comments until you've looked over the proof.
Proof
(1) -20 = -20
(2) 16 - 36 = 25 - 45
(3) 42 - 36 = 52 - 45
(4) 42 - 36 + (9/2)2 = 52 - 45 + (9/2)2
(5) (4 - 9/2)2 = (5 - 9/2)2
(6) 4 - 9/2 = 5 - 9/2
(7) 4 = 5.
SPOILER: Don't read comments until you've looked over the proof.
posted by Moi at 1:32 p.m.
1 Comments:
Step 5->6 is wrong. The square root of a number a^2 is +a and -a. So while step 5 is correct, step 6 is not the correct solution since (+a)^2 = (-a)^2.
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