Why is $\sqrt{ab}$ = $\sqrt{a}\sqrt{b}$ not true when a and b are both negative?
3712
Why $\sqrt{-1 \cdot {-1}} \neq \sqrt{-1}^2$?
60261
Is $\sqrt{x^2}=|x|$ or $=x$? Isn't $(x^2)^\frac12=x?$
98496
Let $a,b \in \mathbb{Q^{+}}$ then $\sqrt{a} + \sqrt{b} \in \mathbb{Q} $ iff $\sqrt{a} \in \mathbb{Q}$ and $\sqrt{b} \in \mathbb{Q}$
22129
Why is $\sqrt{\sum_{i=1}^n |v_i|^2} \leq \sum_{i=1}^n |v_i|$ true?
73079
Eliminating non-integer solutions to $ab / (2\sqrt{ab} + a + b)$
3955
Square roots -- positive and negative
46831
Show that $ a，b, \sqrt{a}+ \sqrt{b} \in\mathbb Q \implies \sqrt{a},\sqrt{b} \in\mathbb Q $
12927
$A^2+B^2=AB$ and $BA-AB$ is non-singular
121700
If $a$ and $b$ are positive real numbers, then $a + b \geq 2 \sqrt{ab}$.
107390
Why is (-1)(-1) = 1?
131844
When does $(e^a)^b = e^{ab}$ hold?
20593
Show that if $a \neq b$ and a and b are positive then $\frac{a}{b}+\frac{b}{a}$ is never an integer
17532
Why does Simplify[b-a] give -a+b and not b-a?
89190
Why is it true that $|AB:A|=|B:A\cap B|$ even if $A$ is not normal in $AB$? (Second Isomorphism Theorem)
103987
What does the square root of minus $i$ equal?
82630
How is it, that $\sqrt{x^2}$ is not $ x$, but $|x|$?
59818
Why $(-2)^{2.5}$ isn't equal to $((-2)^{25})^{1/10}$?