Clueless on how to prove $\|(a,b)\| \le |a|+|b|$
22237
Proof of triangle inequality
39708
Proving $(A\le B)\vee (B\le A)$ for sets $A$ and $B$
11168
Proof of divisibility: if $a|b$ and $a|(b+c)$ then $a|c$
49296
Prove $|(1+|u|^2)v-(1+|v|^2)u|>|u\bar{v}-\bar{u}v|$
42976
How do you prove the follwing $|\sqrt[n]{x}-\sqrt[n]{y}| \le \sqrt[n]{|x-y|}$
84946
If $0<a<b$, prove that $a<\sqrt{ab}<\frac{a+b}{2}<b$
69921
Prove that: $(1+a_1)(1+a_2)...(1+a_n) \le 1 + S_n + (S_n)^2/2! + ... + (S_n)^n/n!$
8027
How to prove $\sqrt{x + y} \le \sqrt{x} + \sqrt{y}$?
72470
Prove that $2|ab| \leq a^2 + b^2$ and $|a|+|b| \leq \sqrt {2}(a^2+b^2)^{1/2}$
143979
How can I prove that $|A| + |B| = |A\cup B| + |A\cap B|$?
89838
Prove that $3 \le a+b+c \le 2\sqrt{3}$ in a triangle
110703
How Can I prove (a+b) mod m = (a mod m) + (b mod m)) mod m?
107774
Prove $\|x\|_1\le \sqrt n \|x\|_2$
10859
Prove $\sup(f+g) \le \sup f + \sup g$
118507
Prove $\frac{ab}{1+c^2}+\frac{bc}{1+a^2}+\frac{ca}{1+b^2}\le\frac{3}{4}$ if $a^2+b^2+c^2=1$
88687
Proof of the inequality $||a+b|^p - |a|^p| \leq \epsilon |a|^p + C_{\epsilon} |b|^p$
80095
Show $|a|+|b|+|c|+|a+b+c| \geq  |a+b|+|b+c|+|c+a|$ for complex $a$, $b$, $c$