Under what conditions is $|x+y|=|x|+|y|$ true?
56954
Equality holds in triangle inequality iff both numbers are positive, both are negative or one is zero
127296
prove that a|b and b|a iff a=+-b
5595
$x^y = y^x$ for integers $x$ and $y$
63854
How do boolean operators work in 'if' conditions?
157733
Are positive real numbers $x,y$ allowed to be taken out during this proof?
74312
If Y is complete then B(X,Y) is complete
96153
$ x^3<y^3 \iff x<y $ proof issue.
7775
Show that $|x-y|\leq |x|+|y|$.
99610
The difference between += and =+
31937
How do I prove equality of x and y?
2315
How to prove that $\lVert x + y\rVert = \lVert x\rVert + \lVert y \rVert \implies \lVert tx + (1-t)y\rVert = t\lVert x\rVert + (1-t)\lVert y \rVert$?
38967
What is the precedence of the + (plus) operator in Java?
73253
Question About equal signs in Theorems
105367
Proving $||\vec{a}+\vec{b}|| = ||\vec{a}-\vec{b}|| \iff \vec{a} \perp \vec{b}$
3820
Prove that $||x|-|y||\le |x-y|$
45370
Is it true that $|d(x, z) - d(y, z)| \leq d(x, y)$ and how do I prove it?
59239
For non-zero real $x$, $y$, $z$ and complex $a$, $b$, $c$ with $|a|=|b|=|c|$, if $x+y+z=0=ax+by+cz$, then $a=b=c$