How Does Row Reduction Show that det(H) = 0 for Matrix H = Q - nI?

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PLEASE HELP! a matrix proof..

Hey!

I really need help with this question if possible.

Let Q be an n x n matrix with each entry = 1
Let I be the n x n identity matrix
let H = Q-n*I
show that det(H) = 0

(hint: think of row reducing H)

Thanks a lot,
j3n
 
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The hint pretty much tells you what to do. This might help: What is the sum of each column?
 

Thread 'Prove that the integral is equal to ##\pi^2/8##'

Prove $$\int\limits_0^{\sqrt2/4}\frac{1}{\sqrt{x-x^2}}\arcsin\sqrt{\frac{(x-1)\left(x-1+x\sqrt{9-16x}\right)}{1-2x}} \, \mathrm dx = \frac{\pi^2}{8}.$$ Let $$I = \int\limits_0^{\sqrt 2 / 4}\frac{1}{\sqrt{x-x^2}}\arcsin\sqrt{\frac{(x-1)\left(x-1+x\sqrt{9-16x}\right)}{1-2x}} \, \mathrm dx. \tag{1}$$ The representation integral of ##\arcsin## is $$\arcsin u = \int\limits_{0}^{1} \frac{\mathrm dt}{\sqrt{1-t^2}}, \qquad 0 \leqslant u \leqslant 1.$$ Plugging identity above into ##(1)## with ##u...
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