Teacher2Teacher

Q&A #104

Teachers' Lounge Discussion: Factoring trinomials

T2T || FAQ || Ask T2T || Teachers' Lounge || Browse || Search || T2T Associates || About T2T

View entire discussion
[<< prev] [ next >>]

From: Thunder

To: Teacher2Teacher Public Discussion
Date: 2002090222:48:53
Subject: Factoring 35x^2-88x+45

To factor 35x^2 - 88x + 45 List the factors of the 'a' term vertically: 1 5 7 35 35 7 5 1 List the factors of the 'c' term vertically: 1 3 5 45 15 9 Now cross multiply each set of 'a' factors with each set of 'c' factors. Since 'c' is positive, you ADD these two products to find the sum of 88. I use a giant T to visualize. (If 'c' were negative, you would SUBTRACT the two products.) a = 35 | c = 45 --------------|------------- 1 5 7 35 | 1 3 5 35 7 5 1 | 45 15 9 -----|----- In this case we use the factors: 7 | 5 5 | 9 7 x 9 = 63 5 x 5 = 25 ---- 88 Now you read the factors across the T as such: (7x - 5)(5x - 9) Since the 'b' term is negative, the second term in each binomial is also negative.

Post a reply to this message
Post a related public discussion message
Ask Teacher2Teacher a new question


[Privacy Policy] [Terms of Use]

_____________________________________
Math Forum Home || The Math Library || Quick Reference || Math Forum Search
_____________________________________

Teacher2Teacher - T2T ®
© 1994- The Math Forum at NCTM. All rights reserved.
http://mathforum.org/