# 20/20 Function Domains — The tutor in your pocket.

> Educational app for finding domains of rational and radical functions. (iPhone/iPad app by Walter Kissach.)

- Source: https://appshunter.io/ios/app/2020-function-domains/id312300527 (this page in markdown: same URL + `.md`)
- Developer: [Walter Kissach](https://appshunter.io/developer/293232788)
- Category: Education, Reference
- Price: $0.99
- Rating: 2.25/5 from 4 App Store ratings · 1 written reviews indexed
- Age rating: 4+
- Requires: iOS 18.0 · 2 MB
- Languages: English
- Released: 2009-04-20
- Data updated: 2026-06-10
- Monetization: paid
- User reviews in markdown: https://appshunter.io/ios/app/2020-function-domains/id312300527/reviews.md

## What is 20/20 Function Domains?

A power learning aid combines Coaching Calculators and Guides to help students find the domains of simple rational functions and radical functions. 

The Coaching Calculator covers rational functions such as :

f(x) =  (3x + 6)/9
f(x) =  (x² - 4)/(3x + 6)
f(x) =   (x² - 9)/(2x² + 4x - 6)

and radical functions such as :

f(x) = √(2x + 6)
f(x) = √((x² - 5x + 6)

Domains are given in set-builder and interval notation.

The Guide also looks at radical functions such as : 

f(x) = -2/√(x - 3)
f(x) = (2x + 3)/(x - √(x + 2))

It's ideal for students as the menu design reinforces each problem solving step.

Examples highlight and simplify algebra that students find hard.

## Key features

- Coaching calculators for rational functions
- Guides for radical functions
- Set-builder and interval notation for domains
- Step-by-step problem-solving reinforcement
- Algebra simplification examples

## Recent user reviews (1 of 1)

All indexed reviews: https://appshunter.io/ios/app/2020-function-domains/id312300527/reviews.md

### 1/5 — Frankillnem

*2019-03-08*

This app is not worth buying, it does not provide you with the information needed.

## Frequently asked questions about 20/20 Function Domains

### What types of functions does 20/20 Function Domains help with?

20/20 Function Domains assists with finding the domains of simple rational functions and various radical functions, including those with complex expressions in the numerator or denominator.

### How does 20/20 Function Domains present domain solutions?

The app provides domains in both set-builder notation and interval notation, catering to different mathematical conventions and student preferences.

### Is 20/20 Function Domains suitable for beginners?

Yes, the app's menu design reinforces each problem-solving step, and its examples highlight and simplify algebra that students often find difficult, making it ideal for learners.

### What devices support 20/20 Function Domains?

20/20 Function Domains is available for iPhone and iPad devices.

### How often is 20/20 Function Domains updated?

The latest version, 7.2, was last updated on September 17, 2025, indicating recent development and potential for ongoing support.

### What is the price of 20/20 Function Domains?

20/20 Function Domains is a paid application, priced at $0.99.

### Does 20/20 Function Domains have ads?

No, 20/20 Function Domains does not contain advertisements. It is a completely ad-free experience.

### What is the user sentiment for 20/20 Function Domains?

Based on the available data, 20/20 Function Domains has a rating of 2.3 stars from 4 ratings, suggesting mixed user reception.

## Version history (last 5 releases)

### 7.2 — 2025-09-17

This version is iOS 18 compatible and contains minor bug fixes.

### 7.1 — 2024-04-06

iOS 17 compatibility and minor bug fixes.

### 7.0 — 2021-10-10

Minor user interface bug fixes.

### 6.9 — 2021-10-06

iOS 15 compatibility and minor bug fixes.

### 6.8 — 2021-09-05

Minor bug fixes.

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## More apps by Walter Kissach

- [Quadratic Inequalities](https://appshunter.io/ios/app/quadratic-inequalities/id293232785)
- [Circles and Equations](https://appshunter.io/ios/app/circles-and-equations/id293619582)
- [Even and Odd Polynomials](https://appshunter.io/ios/app/even-and-odd-polynomials/id293668394)
- [Quadratic Factoring](https://appshunter.io/ios/app/quadratic-factoring/id294040055)
- [Quadratic Equations](https://appshunter.io/ios/app/quadratic-equations/id294195555)
- [20/20 Fraction Basics](https://appshunter.io/ios/app/2020-fraction-basics/id298766849)

All apps by Walter Kissach: https://appshunter.io/developer/293232788

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*Data collected daily from the US App Store and indexed by [AppsHunter](https://appshunter.io/). User reviews are verbatim App Store reviews. Ratings, prices and chart positions refresh continuously; this snapshot is from 2026-06-10.*