1
$\begingroup$

Hi guys I'm making Patrick Star for a graphing project.

Anyways I'm using a parabola for his head on my TI-84 but when I set limits on it, it graphs a straight line.

So the equation itself is $y=(-0.5(x+1)^2+9)$ and I set limits to {$2.7$ is greater than $x$} and {$-6.9$ is less than $x$}

At $x=2.7$ it makes a horizontal line to infinity and at $x=-6.9! it makes another horizantal line to negative infinity.

Does anyone know how i can stop this?

$\endgroup$
  • $\begingroup$ try it with www.wolframalpha.com/ I'm pretty sure it's just a glitch in the inner mechanisms of the calculator to make calculation faster $\endgroup$ – shai horowitz May 22 '16 at 21:23
0
$\begingroup$

It's not clear exactly what you did. If you were doing something like

Y = (-0.5(X+1)² + 9)(2.7>X)(-6.9<X)

then this will cause the value of Y to be zero when X is outside the selected range (because one of the two operators > or < will produce the value $0$), but it will not make the value of Y be undefined, which is what you want.

You might try parametric graphing. For example:

X = T
Y = -0.5(T+1)² + 9

and for the WINDOW variables,

Tmin = -6.9
Tmax = 2.7

(Caveat: I'm inferring all of this from the TI-84 manual and from hints at https://answers.yahoo.com/question/index?qid=20080612194029AAThWAe. I don't have the actual calculator on hand to try it, so you may need to do a little experimenting. For example, will the calculator allow you to set Tmin to a negative number?)

$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.