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 July 12th, 2019, 08:57 PM #1 Member   Joined: Aug 2018 From: România Posts: 88 Thanks: 6 A grade three equation Hello all, Solve the equation $\displaystyle x^3-\{x \}^2+i[x]-1=0$ where $\displaystyle i^2=-1$. All the best, Integrator
 July 13th, 2019, 02:56 AM #2 Global Moderator   Joined: Dec 2006 Posts: 20,969 Thanks: 2219 What do $\{x\}$ and $[x]$ mean in your equation?
 July 13th, 2019, 07:49 AM #3 Senior Member   Joined: Feb 2016 From: Australia Posts: 1,838 Thanks: 653 Math Focus: Yet to find out. That’s some smart 3rd graders Thanks from SDK and Greens
July 13th, 2019, 01:11 PM   #4
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Quote:
 Originally Posted by Joppy That’s some smart 3rd graders
I assumed they meant 3rd-order.

I can give you the engineering solution (attached).
Attached Images
 3rdOrder.png (16.3 KB, 1 views)

July 13th, 2019, 10:03 PM   #5
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Quote:
 Originally Posted by skipjack What do $\{x\}$ and $[x]$ mean in your equation?
Hello,

$\displaystyle x=[x]+\{x\}$.Par exemple $\displaystyle [-3.7]=-4$ and $\displaystyle \{-3.7\}=0.3$.

All the best,

Integrator

Last edited by Integrator; July 13th, 2019 at 10:11 PM.

July 13th, 2019, 10:10 PM   #6
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Quote:
 Originally Posted by DarnItJimImAnEngineer I assumed they meant 3rd-order. I can give you the engineering solution (attached).
Hello,

How did You calculate?Thank you very much!

All the best,

Integrator

July 14th, 2019, 07:40 AM   #7
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Quote:
 Originally Posted by Integrator Hello, [MATH]$\displaystyle \{-3.7\}=0.3$. All the best, Integrator
did you mean 0.7?

July 14th, 2019, 08:01 AM   #8
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Quote:
 Originally Posted by romsek did you mean 0.7?
Hello,

No!If $\displaystyle [-3.7]=-4$ , then $\displaystyle \{-3.7\}=0.3$.

Al the best,

Integrator

July 14th, 2019, 09:03 AM   #9
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Quote:
 Originally Posted by Integrator How did You calculate?
I didn't; I asked MATLAB to do it for me. Of course, that was before I knew what [x] and {x} meant in your equation.

 July 14th, 2019, 10:06 AM #10 Global Moderator   Joined: Dec 2006 Posts: 20,969 Thanks: 2219 What definitions apply if $x$ isn't real? If $x$ has to be real, $0 < x < 1$, in order that $[x]= 0$, but there are no values of $x$ in that range that satisfy the equation.

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