



 
A trinomial of this type may be factored by decomposition. The initial goal is to break down (decompose) the middle term of +20x into two terms so that we can proceed to factor by grouping the resulting 4 terms. In order to properly break down the +20x we need to examine the coefficient on x^{2} and the constant. If we multiply these numbers we get (3)(7) = 21. We must find two numbers whose:
The two numbers we want are +21 and 1. Proceed as follows:
This method of decomposition is useful for factoring a trinomial when the x^{2} term of the trinomial is not 1. Hope this helps, Leeanne  


Math Central is supported by the University of Regina and The Pacific Institute for the Mathematical Sciences. 