We may now factor out the . Take the time to memorize the special polynomial forms involving difference of two squares, sum of two cubes, and difference of two cubes. These forms occur frequently throughout the remainder of this course and you will save yourself time in factoring by recognizing these forms and knowing the formulas. Try grouping together the first pair of terms and the second pair of terms with addition separating the first pair from the second pair. We group the first pair of terms and the second pair of terms.
Most teachers use a trial and error method to factor an expression involving three terms.
There is an alternative method that does not use as much trial and error. If you struggle with the trial and error method, you may find this method more convenient. Rewrite the polynomial so its middle term bx is written as a sum of two terms whose coefficients are the two numbers found in step 2. The trinomial has the form where . Look at pairs of numbers whose product is and then find their sum.