The absolute value explained step by step

This is probably the best video to teach absolute value equations.
https://www.youtube.com/watch?v=h16ZBhHalbw

La geometría en el arte

Genial vídeo sobre geometría en el arte.
https://www.youtube.com/watch?v=baSuNdUk1BI

Trabajando con rotaciones de un cuerpo

Para trabajar las rotaciones de un cuerpo sobre un punto de rotación, nada mejor que hacerlo con una ficha como esta:
http://imageneso.blogspot.com/2014/10/transformaciones-geometricas-giro.html

Equations with Absolute Values

Equations = One or no solution.
Inequalities = Multiple solutions.
Equations with Absolute Values = 2 solutions (+ and -).

Absolute value:
http://www.mathsisfun.com/numbers/absolute-value.html

Absolute value in Algebra:
http://www.mathsisfun.com/algebra/absolute-value-solving.html

Example: how to solve an absolute value on an equation:
https://www.khanacademy.org/math/algebra/solving-linear-equations-and-inequalities/absolute-value-equations/v/absolute-value-equation-example

Using The GIMP to teach translation, rotation and other transformations

The GIMP is very useful to teach some concepts of transformations in Geometry.
Download it for free here:
http://www.gimp.org/

The ultimate resources for inequalities

This is a game to practice inequalities in your class.
http://www.math-play.com/Inequality-Game.html

Inequalities (properties)
https://www.mathsisfun.com/algebra/inequality-properties.html

Solving linear inequalities made easy
https://www.youtube.com/watch?v=0X-bMeIN53I

El precio de no saber matemáticas

http://educapdi.blogspot.com.es/2015/05/el-alto-precio-de-no-saber-matematicas.html