Why is it not possible to simplify $b=(X'X)^{-1}X'y$
30781
Why the representation in the form of $Z'X(X'X)^{-1}X'Z$ can not be simplified into $Z'Z$
107390
Why is (-1)(-1) = 1?
67588
Why does $|e^{ix}|^2 = 1$?
80471
Derivative of $(y-XB)' h(y-XB)$ with respect to $B$
33184
Something strange about $\sqrt{ 4+ \sqrt{ 4 + \sqrt{ 4-x}}}=x$ and its friends
24307
Is $x^x=y$ solvable for $x$?
43537
How can $x^2y''-3xy'+3y=0$ be solved?
3712
Why $\sqrt{-1 \cdot {-1}} \neq \sqrt{-1}^2$?
78736
Check my proof that $(ab)^{-1} = b^{-1} a^{-1}$
88374
How to separate variables in DiffEq of $y'=x-y$
8276
How do I get my equation to have the form $(x-a)^2 + (y-b)^2 + (z-c)^2-d = 0$?
134075
Inverse of $A^{-1}+B^{-1}$
108923
What is wrong with this false proof? $-1=(-1)^1=(-1)^\frac{2}{2}=((-1)^2)^\frac{1}{2}=\sqrt{(-1)^2}=\sqrt{1}=1$
82097
If $A \succeq B$, is it true that $B^{-1} \succeq A^{-1}$?
106934
$x^x=y$. How to solve for $x$?
154829
How to solve $y'' + y = y^{-3}$
28502
How to solve $x^3=-1$?