$${\mathtt{X}} = {{\mathtt{Y}}}^{{\mathtt{2}}}{\mathtt{\,-\,}}\left({\mathtt{10}}{\mathtt{\,\times\,}}{\mathtt{Y}}\right){\mathtt{\,\small\textbf+\,}}{\mathtt{40}}$$
+33661 This is just a quadratic on its side. See if the following helps:
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+118673 Thanks Alan,
X=Y^2-(10Y)+40
This is a sidways parabola. I know because it is the y that is squared.
It opens out in the positive direction. I know that because the coefficient of y^2 is 1 which is POSITIVE.
Now if I can get it into the form
$$(y-k)^2=4a(x-h)$$
then the vertex will be (h,k)
$$\\X=Y^2-(10Y)+40\\\\
X-40=Y^2-(10Y)\\\\
Y^2-(10Y)=X-40\\\\
Y^2-(10Y)+25=X-40+25\qquad $I have completed the square$\\\\
(Y-5)^2=X-15\\\\
$Vertex is (15,5)$$$
This the same answer as shown in Alan's graph. :)
+1316 Hi Alan and Melody
When I put this equation in Desmos graph it show the parabola going up instead of side ways like Alan’s graph
It show it going up for all thes equations
X(Y)=Y^2-(10Y)+40
X=Y^2-(10Y)+40
Y=X^2-(10X)+40
it also do it when I leave out the X= part
If I put the colon : in like Alan put in his then it do not work at all. It give an exclamation point!
Can you please show me how to make this work in Desmos graph ?
+129852 It seemed to work OK for me, Dragonlance .......(???)
Here's the graph.......https://www.desmos.com/calculator/sq4i2l2dtk
+1316 Thank you CPhill
I made a new post
http://web2.0calc.com/questions/desmos-sometimes-not-work-right-if-you-use-capital-letters
to show what the problem was.
+33661 Dragonlance wrote: "If I put the colon : in like Alan put in his then it do not work at all..."
I used Mathcad to do that calculation. In Mathcad (and some other sorts of mathematical software, like Maple, for example) := is used to represent assignment. This is not the case for all calculational software, and it clearly doesn't work as an assignment operator in Desmos, where a simple = is all that is necessary.
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+1316 Thank you Alan. My TI NSpire use the := for some kind of varables.
Does Mathcad treat capital letter VARABLES different than small letter varables ?
+33661 Mathcad treats upper and lower case as indicating different variable names, but it doesn't make any assumption about which one should go where on a graph; it leaves that up to the user to decide.
I'd forgotten that the TI_NSpire uses := as well (I have the software-only version, not the physical calculator, and I don't use it very often).
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