What does $QAQ^{-1}$ actually mean? - Mathematics Stack Exchange I'm self-learning Linear Algebra and have been trying to take a geometric approach to understand what matrices mean visually I've noticed this matrix product pop up repeatedly and can't seem to de
abstract algebra - Prove that 1+1=2 - Mathematics Stack Exchange Possible Duplicate: How do I convince someone that $1+1=2$ may not necessarily be true? I once read that some mathematicians provided a very length proof of $1+1=2$ Can you think of some way to
How can 1+1=3 be possible? - Mathematics Stack Exchange So that's the "proof" The failure is at step 5, where you say that pq = pr p q = p r implies that q = r q = r; that's true only if you know p p is nonzero For instance 0 ⋅ 5 = 0 ⋅ 7 0 ⋅ 5 = 0 ⋅ 7, but that doesn't let you conclude that 5 = 7 5 = 7, because 0 0 has no multiplicative inverse In your case, the number b − a b − a is playing the role of p p, and because b b and a a