Free Printable Math Worksheets -- Eraserdog.com kidfriendlymath Cleave Books Math Printable Worksheets Factoring a Quadratic Trinomial by Grouping Another method for factoring these kinds of quadratic trinomials is called factoring by grouping. Factoring by grouping can be a bit more tedious, and is often not worth the trouble if you can find the correct factors by some quick trial and error. However, it works quite well when the factors are not immediately obvious, such as when you have a very large number of candidate factors. When this happens, the trial and error method becomes very tedious Factoring by grouping is best demonstrated with a few examples. Example: The Procedure Given a general quadratic trinomial ax2 + bx + c 1. 2. hk = ac (h and k are factors of the product of the coefficient of x2 and the constant term) h + k = b (h and k add to give the coefficient of x) 3. ax2 + hx + kx + c 4. (ax2 + hx) + (kx + c) x(ax + h) + (kx + c) (note: because of the way you chose h and k, you will be able to factor a constant out of the second parentheses, leaving you with two identical expressions in parentheses as in the examples).
Colin Foster The Story of Mathematics - A History of Mathematical Thought from Ancient Times to the Modern Day Geometric Shapes. Your One Stop Basic Geometry Resource isotropic.org > polyhedra models Here are templates for making paper models for each of the 5 Platonic solids and the 13 Archimedean semi-regular polyhedra. You are free to use them for any non-commercial purpose, as long as the copyright notice on each page is retained. Here's a complete set of the Archimedean polyhedra: I think that they are pretty straightforward to assemble without any instructions — just cut them out carefully, fold along the black lines, and tape. For best results, print these templates out on cardstock, or print them on regular paper and use a pin to transfer the template to something heavier. All of the models have a common edge length, so relative sizes are meaningful. Start by making the Platonic solids and the smaller Archimedeans first. If you don't have it already, you'll need the free Adobe Acrobat Reader. Platonic solids (3,3,3) tetrahedron (4,4,4) cube (3,3,3,3) octahedron (3,3,3,3,3) icosahedron These four all fit on the same page; by printing out one copy of the page you can make them all.