# Dr Matrix's math problem **URL:** \ **Category:** Factual Questions\ **Created:** [June 4, 2003, 1:15pm UTC](https://boards.straightdope.com/t/dr-matrixs-math-problem/179578 "2003-06-04T13:15:19Z")\ **Posts on this page:** 5\ **Page:** 1
**Author:** ![smiling\_bandit](https://avatars.discourse-cdn.com/v4/letter/s/e9a140/32.png) [@smiling\_bandit](https://boards.straightdope.com/u/smiling_bandit)\ **Post date:** [June 4, 2003, 1:15pm UTC](https://boards.straightdope.com/t/dr-matrixs-math-problem/179578/1 "2003-06-04T13:15:19Z")
Dr. Matrix put this is a thread in the Pit, about abolishing math (apparently “proving” 1=2). Let a = b a \* b = b \* b – multiply by b a \* b - a \* a = b \* b - a \* a – subtract a \* a a(b - a) = (b + a)(b - a) – factor a = b + a – divide by common factor (b - a) a = a + a – substitution a = 2a – combine 1 = 2 – divide by common factor a The problem is I can’t figure out what’s wrong with this! Which, is very irritating. What am I missing?! Geez, I can estimate values very accurately, but I hate these problems. ---
**Author:** ![Q.E.D](https://avatars.discourse-cdn.com/v4/letter/q/51bf81/32.png) [@Q.E.D](https://boards.straightdope.com/u/Q.E.D)\ **Post date:** [June 4, 2003, 1:17pm UTC](https://boards.straightdope.com/t/dr-matrixs-math-problem/179578/2 "2003-06-04T13:17:34Z")
Divison by zero. Since a = b, a - b =0, therefore dividing by (a - b) is dividing by zero, and thus undefined. ---
**Author:** ![Jabba](https://avatars.discourse-cdn.com/v4/letter/j/b5e925/32.png) [@Jabba](https://boards.straightdope.com/u/Jabba)\ **Post date:** [June 4, 2003, 1:31pm UTC](https://boards.straightdope.com/t/dr-matrixs-math-problem/179578/3 "2003-06-04T13:31:58Z")
In slightly more detail: From the fact that a_b = a_c we can, if a is not 0, deduce that b = c. However, the statement 0_b = 0_c (1) is true for every b and c. What **Dr Matrix** did was to prove an equation of the form (1) and infer ( fallaciously) that b = c. ---
**Author:** ![smiling\_bandit](https://avatars.discourse-cdn.com/v4/letter/s/e9a140/32.png) [@smiling\_bandit](https://boards.straightdope.com/u/smiling_bandit)\ **Post date:** [June 4, 2003, 1:45pm UTC](https://boards.straightdope.com/t/dr-matrixs-math-problem/179578/4 "2003-06-04T13:45:34Z")
Ah. Cute. Thanks a lot, this one was bugging me since it didn’t seem to be a bait-and-switch problem and it looked like it was following “the rules” properly. ---
**Author:** ![Angua](https://avatars.discourse-cdn.com/v4/letter/a/8baadc/32.png) [@Angua](https://boards.straightdope.com/u/Angua)\ **Post date:** [June 4, 2003, 2:02pm UTC](https://boards.straightdope.com/t/dr-matrixs-math-problem/179578/5 "2003-06-04T14:02:03Z")
> [@](#): > > \*Originally posted by smiling bandit \* > \*\*Dr. Matrix put this is a thread in the Pit, about abolishing math (apparently “proving” 1=2). > > \ > > a \* b - a \* a = b \* b - a \* a – subtract a \* a > > \ > \*\* And in this line, we prove that 0 = 0, since if a = b, then a_b - a_a = b_b - a_a =\> a_a - a_a = a_a -a_a =0 Hence proving why **Dr Matrix’s** arguments are fallacious from the get-go.