May 30, 2016

Homework Help: Algebra Zero Product Rule

Posted by Jake on Saturday, September 2, 2006 at 3:56pm.

I'm working with the zero product rule and I've somehow lost my way on a certain problem pattern.

(x+8)(x-3)= -30

Is the pattern and the answer in the book says -2 or -3, but when I do the problem...

x+5x-24= -30
x+5x+6= 0
x= -6 x= 1

That is how I factored it. It just doesn't comply with the book... Does anyone have a correct solution? The rest of my problems are in this pattern. :(

Your factorization is not correct
(x+6)(x-1) =x^2+5x-6 not x^2+5x+6 as it should.
Try factoring again. Sometimes the book can have a typo, but not here.

Hrm, again I get x= -6 or x= 1. Maybe it is just a typo in the book. It's my first time factoring a problem with such a pattern too.

No, it's not a typo, Try putting the values x=-2,-3 into your original equation and test them. Then try factoring the equation
x+5x+6 = 0 again.

Oh, I get it. Though now I wonder if I factored like I did last time if it would have been marked wrong on an exam since it does factor.


It's easy to get the factor wrong, that's why you should test your work when you're done. I hope you factored this one as
(x+2)(x+3)=0 so x=-2 and x=-3 are the solutions. Be sure to multiply the terms out as a check -if you have time on a test.

Excellent, I didn't know I could check my problems like that. The book was giving me alternate instructions to check my work, but that is clearly quicker and simple. Not time consuming at all.

Yes, it would have been marked wrong because it does NOT factor as you had it. Try what Roger suggested. Put your factors in and see if they satisfy the equation. The factors you had will not.

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