Melody

Mon 11/8/14

Interesting little 3D/algebra question.

@@ End of Day Wrap :      Sun 10/8/14      Sydney, Australia     Time 7:10  pm  

Hi all,

It was a very quiet Sat/Sun today.  There were a few good answers given by AzizHusain, Alan and CPhill. Thanks for those. 

Here are a couple of interest threads.

* Complicated 'quadratic' equation - extension question, for interest only.

Thanks Alan,

I'll spend more time in it. 

Thanks Alan. 

Why is that true Alan?

Is there something obvious that I am missing?

$${\mathtt{16}}{\mathtt{\,\times\,}}{{\mathtt{t}}}^{{\mathtt{2}}}{\mathtt{\,-\,}}{\mathtt{105}}{\mathtt{\,\times\,}}{\mathtt{t}}{\mathtt{\,\small\textbf+\,}}{\mathtt{34}} = {\mathtt{0}} \Rightarrow \left\{ \begin{array}{l}{\mathtt{t}} = {\mathtt{\,-\,}}{\frac{\left({\sqrt{{\mathtt{8\,849}}}}{\mathtt{\,-\,}}{\mathtt{105}}\right)}{{\mathtt{32}}}}\\
{\mathtt{t}} = {\frac{\left({\sqrt{{\mathtt{8\,849}}}}{\mathtt{\,\small\textbf+\,}}{\mathtt{105}}\right)}{{\mathtt{32}}}}\\
\end{array} \right\} \Rightarrow \left\{ \begin{array}{l}{\mathtt{t}} = {\mathtt{0.341\: \!589\: \!889\: \!970\: \!270\: \!7}}\\
{\mathtt{t}} = {\mathtt{6.220\: \!910\: \!110\: \!029\: \!729\: \!3}}\\
\end{array} \right\}$$

If you want to do it by hand use the quadratic formula 

a=16, b=-105 and c=34

If you do not know the quadratic formula, here it is.

I'm going to do the last one  

$$y=\sqrt{25-x^2}\\
when\; x=4\\
y=\sqrt{25-16}=\sqrt9=3$$

So you have a rectangle with length 2 units and height 3 units.

So the area is 2*3=6u^2

You can probably do this on the web2 calc as well but i don't know how.

anyway, I got you the answer. 

This question doesn't make sense. 

I didn't know that Chris.  Thanks