Where does this proof that $1 = 2$ go wrong? (Expressing $x^2=\sum_{n=1}^xx$ and differentiating)
1002
Where is the flaw in this "proof" that 1=2? (Derivative of repeated addition)
146533
Having problems proving $ \sum_{r=0}^{n}(r+1) \binom{n}{r} = (n+2)2^{n-1} $
108923
What is wrong with this false proof? $-1=(-1)^1=(-1)^\frac{2}{2}=((-1)^2)^\frac{1}{2}=\sqrt{(-1)^2}=\sqrt{1}=1$
121544
Proof by Induction: $2(\sqrt{n+1} - \sqrt{n}) < \frac{1}{\sqrt{n}} < 2(\sqrt{n}-\sqrt{n-1})$
142513
Prove that $2xy\mid x^2+y^2-x$ implies $x$ is a perfect square.
134122
When is differentiating an equation valid?
75387
A proof that $1=2$. May I know why it’s false?
142132
How do you prove $\sum \frac {n}{2^n} = 2$?
5272
Proving that $\sum_{k=0}^{n}\frac{(-1)^k}{{n\choose k}}=[1+(-1)^n] \frac{n+1}{n+2}.$
57407
Show that $(x^2 + y^2) \sin\left(\frac{1}{x^2 + y^2}\right)$ is differentiable.
147111
Where is the Proof for the Sum-to-Product rule derrived from?
38995
Induction proof that $\sum_{j=n}^{2n-1} (2j + 1) = 3n^2$ - what happened?
61604
$V = V_1 + V_2$ confusion? Why is my "proof "incorrect?
131140
Understanding ProofWiki's proof of differentiation of sine power series
72026
Induction proof of $\sum_{k=1}^{n} \binom n k = 2^n -1 $
34758
Cancellation Law for Direct Sums - What is wrong with this argument?
150642
How to prove $\sum^n_{i=1} \frac{1}{i(i+1)} = \frac{n}{n+1}$?