Posted by Denis Borris on November 11, 2002 at 15:32:53:
In Reply to: Factoring trinomials posted by Mark Gober on November 11, 2002 at 14:48:02:
: On the page about factoring trinomials (/20991/alg/factoring.html#factoring) it gives you 4 rules about them. I contend that rule #3 is not always true. If you do the quiz, it'll prove my point. Rule #3 states that The coefficient of the middle term of the trinomial is the sum of the last terms of the binomials. The following problem was on the quiz and didn't fit that rule.
: #4
: 2x^2 + 3x + 1
: Factor.
: (2x+1)(x+1)
: 1+1 does not equal 3.
: For the most part rule number 3 holds true, but not all the time. If i'm doing something wrong please tell me. If you concur at least tell me so that i don't check myself into an asylum. This has had me stumped for over an hour.
This is a "do not adjust your set" thing;
your 1's are multiplied by the coefficients of x: 1*2 + 1*1 = 3;
all quite misleading, since a straight add works if the coefficients of x are both 1,
since multiplying by 1 is redundant....
(ax + b)(cx + d) : a*d + c*b = midterm's coefficient.
Easy nuff to see if you simply do a couple of examples.....
I looked at "(/20991/alg/factoring.html#factoring)"
and it appears that it is understood that the coefficient of X^2 is 1: if that's the
case, then they SHOULD make that clear......