Possible bug with evaluating using fractions in equation

Something’s not working the way it seems like it should.

When I enter the correct value as a fraction

I saw I got marked incorrect

But I expected it to be marked correct.


  1. Using a decimal approximation works.
  2. I have tried different equations to evaluate and I am wondering if there is something going on with distributing by a negative on the right side of the equation.

Here’s the link to the page, dashboard, or activity: Bug?? • Activity Builder by Desmos

And here are some screenshots or a video:

This is actually an error that comes from converting a value into a string and then back into a value.

Due to rounding , you’re left with a very small difference. ~4.4*10^-16

What your absolute value check does is print out this value as a string and interpolate it into another string before taking the numeric value of that “compound” string.

This means the the value of ~0.00000000000000044 is being inserted into the absolute value function as -4.4e-16.

the calculator is interpreting the value of e as 2.71828182846.


You can avoid this by keeping numbers as numbers using simpleFunction.evaluateAt rather than numericValue.

simpleFunction("\left|x\right|").evaluateAt(eq.evaluateAt(v)) would be the closest to what you have, but writing a single function that evaluates only once (absolute value of the difference function) would be more elegant.