Algebra

Fractions

Adding Fractions This activity was built to try to help students visualize adding fractions with different denominators. It's still a work in progress.
Multiplying Fractions A visual representation of multiplying fractions, with sliders for both numerators and denominators.

Functions

Graphing Quadratics in Vertex Form This activity lets students interact with a, h, and k for quadratic functions in vertex form. Unfortunately, Desmos does not have the ability to dynamically label the function.

Inequalities

Absolute Value Inequalities This (very inefficiently) illustrates the solution set to the absolute value inequality |x-a|<b, for limited values of a and b.

It also clearly demonstrates Desmos' primary weakness - the lack of dynamic labeling.
Rational Inequalities A demonstration of rational inequalities, highlighting when the graph is below or above the x-axis. It also highlights the intercept (if there is one) and any vertical asymptotes.

Factoring

Factoring Visual This was a visual I made to demonstrate a quadratic polynomial with all positive terms. A variety of questions could be posed.