# Equations with exponents

**URL:** <https://cl.desmos.com/t/equations-with-exponents/2393>\
**Category:** Questions\
**Tags:** validation, correctness\
**Created:** [January 15, 2021, 1:15am UTC](https://cl.desmos.com/t/equations-with-exponents/2393 "2021-01-15T01:15:29Z")\
**Posts on this page:** 6\
**Page:** 1

<div class="post-metadata">

**Author:** ![Frances\_Janowiak](https://yyz1.discourse-cdn.com/flex031/user_avatar/cl.desmos.com/frances_janowiak/32/1410_2.png) [@Frances\_Janowiak](https://cl.desmos.com/u/Frances_Janowiak)\
**Post date:** [January 15, 2021, 1:15am UTC](https://cl.desmos.com/t/equations-with-exponents/2393/1 "2021-01-15T01:15:29Z")

</div>

I have been looking on google but was not able find what I am looking for.

I am wanting students to be able to solve equations involving exponents and then be able to check for correctness.

A few examples of things I am trying to solve:

4^x = 64 x=3

4^4-5x = 256

2^3x+1 = 4^x x=-1

(x^x+1)(2^3x-4) = 64 x = 3/2

(1/9)^2x-1 (81) = 243 x= 1/4

(125^3y+7)/3125^y) = 15625 y = -15/4

Is something like this possible? I was trying to use the simple function but had no luck. Any assistance is greatly appreciated.

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<div class="post-metadata">

**Author:** ![Daniel\_Grubbs](https://yyz1.discourse-cdn.com/flex031/user_avatar/cl.desmos.com/daniel_grubbs/32/719_2.png) [@Daniel\_Grubbs](https://cl.desmos.com/u/Daniel_Grubbs)\
**Post date:** [January 15, 2021, 3:00am UTC](https://cl.desmos.com/t/equations-with-exponents/2393/2 "2021-01-15T03:00:12Z")

</div>

simpleFunction should work fine for the first, but your others aren’t formatted correctly. You can always type your equation into the graphing calculator then copy and paste it to the CL to see how it should be formatted (i.e. the exponent portion should be surrounded by curly braces).

For example, for your second equation:

```auto
check=simpleFunction("4^{4-5x}").evaluateAt(input.numericValue)=256
correct:check

```

As you’ve written, 4^4-5x = 256 is equivalent to -5x+4^4 =256.

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<div class="post-metadata">

**Author:** ![Frances\_Janowiak](https://yyz1.discourse-cdn.com/flex031/user_avatar/cl.desmos.com/frances_janowiak/32/1410_2.png) [@Frances\_Janowiak](https://cl.desmos.com/u/Frances_Janowiak)\
**Post date:** [January 15, 2021, 2:22pm UTC](https://cl.desmos.com/t/equations-with-exponents/2393/3 "2021-01-15T14:22:57Z")

</div>

Thank you for your response. I am doing something incorrect. I tried putting the code in for a math input and as a table and I am getting errors on both. Could you help me please?

> **[Solving Equations with Exponents • Activity Builder by Desmos](https://teacher.desmos.com/activitybuilder/custom/6001a2ca7d66840b9f648349)**
>
> by Frances Janowiak

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<div class="post-metadata">

**Author:** ![Susan\_Lauer](https://yyz1.discourse-cdn.com/flex031/user_avatar/cl.desmos.com/susan_lauer/32/1832_2.png) [@Susan\_Lauer](https://cl.desmos.com/u/Susan_Lauer)\
**Post date:** [January 15, 2021, 4:47pm UTC](https://cl.desmos.com/t/equations-with-exponents/2393/4 "2021-01-15T16:47:11Z")

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You don’t need anything in the **Note** CL. Try this in the CL for the **Table** :

```auto
f = simpleFunction("4^{4-5x}")
cellContent(1,3): when check "✅" otherwise ""
check=f.evaluateAt(this.cellNumericValue(1,2))=256
correct:check

```

And this for the **Math Input** :

```auto
f=simpleFunction("4^{4-5x}")
check=f.evaluateAt(input1.numericValue)=256
correct:check

```

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<div class="post-metadata">

**Author:** ![Daniel\_Grubbs](https://yyz1.discourse-cdn.com/flex031/user_avatar/cl.desmos.com/daniel_grubbs/32/719_2.png) [@Daniel\_Grubbs](https://cl.desmos.com/u/Daniel_Grubbs)\
**Post date:** [January 15, 2021, 5:32pm UTC](https://cl.desmos.com/t/equations-with-exponents/2393/5 "2021-01-15T17:32:08Z")

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In slide 2, there’s no `correct` sink for a note, so all the code you have in the note should be in the input CL. I made a mistake in my original post (fixed now). It should be `evaluateAt`. Then where I have `input` you need to change to `input1` since that’s the name of your input.

Once you’ve moved your code, if you want your note to have some feedback, you can refer to `input1.script.check` for any when-otherwise statements.

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<div class="post-metadata">

**Author:** ![Frances\_Janowiak](https://yyz1.discourse-cdn.com/flex031/user_avatar/cl.desmos.com/frances_janowiak/32/1410_2.png) [@Frances\_Janowiak](https://cl.desmos.com/u/Frances_Janowiak)\
**Post date:** [January 15, 2021, 6:21pm UTC](https://cl.desmos.com/t/equations-with-exponents/2393/6 "2021-01-15T18:21:46Z")

</div>

Thank you both for your help, I truly appreciate it.