## Discussion

−24 − (x2 − 1)2 =

 (A) − x4 + 2x2 +15 (B) ... (C) ... (D) ... (E) ... (F) ...
*This question is included in Nova Math - Diagnostic: Test / Review, question #6

The solution is

Posted: 01/15/2012 12:23
Hi Pre-eminent Friends
DawnTED says:Brendan is a involved guy, I at any cost he barely has reasonably tempo for the benefit of me so to yield 30 or so lbs in a month
Illinois Most excellently intake veer Impediment influence lustfully
click on
Unhappy Calorie Foods That Briskness Power Ill
Metabolism Secrets
Nutriment fo men
Fantabulous Sellers Upper crust Diets
Fare fo men Blame you bye
Contributor
Posted: 01/15/2012 14:16
-2^4 - ( x^2 - 1 )^2
Now we'll use the distributive property (a-b)^2 = a^2 -2ab + b^2
-2^4 - ( (x^2)^2 - 2x^2 - 1^2 )
-2^4 - ( x^4 - 2x^2 - 1^2 )
-2^4 -x^4 + 2x^2 + 1^2
-x^4 + 2x^2 + 1 - 16
-x^4 + 2x^2 - 15

Niels
Posted: 01/16/2012 16:17
Where does the 2x^2 come from?
Contributor
Posted: 01/16/2012 19:41
Like I said earlier, using the (special case) distributive property, I will show it with FOIL.
(a-b)^2
(a-b)(a-b)
a^2 -ab -ba +b^2
a^2 -ab -ab +b^2
a^2 -2ab +b^2

If you plug in (x^2) for a, and (1) for b, it will get you the -2ab >> -2(x^2)(1) ergo -2x^2

Niels
Posted: 06/20/2012 02:04
I have been studing this problem for about a few mins now hoping to understand where (a) and (b) came from.. I sure you know way more then u do on this topic.. Plz explain?
Posted: 06/20/2012 02:06
Never mind I understand sorry
| Edit
Posted: 01/29/2012 18:25
Where does the -2x^2 came from, and why they changed -1 to positive 1?
Contributor
Posted: 01/30/2012 00:47
Serigne, I guess you didn't look at this forum thread first.
The sign changes done are due the priority rules, parentheses first and when there's a negative sign in front, we distribute the sign over all terms in the parentheses by multiplying each term with -1

8 + ( 5 - 3 + 2 )
8 + (1)( 5 - 3 + 2 )
8 + 5 - 3 + 2
= 12

8 - ( 5 - 3 + 2 )
8 + (-1)( 5 - 3 + 2 )
8 - 5 + 3 - 2
= 4

Niels
Posted: 02/29/2012 17:46
Im not really good in math but im taking the sat ... In march 10th in im really lost
Posted: 10/28/2012 22:16
-2^4 = +16
Not -16
Posted: 10/28/2012 22:19
Posted: 12/04/2012 16:02
Sorry Katie, I think there's something unusual on your answer. It should be (C) instead of (A). I think I know what you did wrong. You have elevated -2 to the fourth power instead of elevating 2 to the fourth power and putting the negative sign. Am I right?
Posted: 03/07/2013 04:51
Yes, exactly.
Posted: 10/28/2012 22:20
Oh never mind
Posted: 11/03/2012 12:51
I don't get where the 2x^2 come from
Posted: 11/03/2012 14:46
Kary, that's just from "foiling" the terms inside the parentheses that are raised to the power of 2, which means they are multiplied by themselves.
Posted: 11/03/2012 14:50
Kary,
(x^2 - 1)^2
=(x^2 - 1) (x^2 - 1)
= x^4 - 2x^2 +1
Hope that helps
Posted: 11/03/2012 16:00
Thanks now I understand
Posted: 03/07/2013 04:48
(-2)^4=16, not -16.
-2*-2*-2*-2=16.
Posted: 05/20/2013 16:29
Mantek, you are right. But that's not what the problem is asking. Not (-2)^4, but -2^4 ....
Posted: 05/19/2013 18:04
Where does the (-1) come from ? 2 doesn't apply as a variable like "x" in an equation so why is there a 1 there ?
Posted: 05/20/2013 16:30
Andres Tirado, the explanation is just showing that a negative sign is the same operation as multiplying a number or variable with -1.
Posted: 05/30/2013 17:33
Are choice B and E the same answer or is there something I'm missing ?
Contributor
Posted: 06/06/2013 22:41
Andres, yes there is something you are missing. Please look more closely.
Posted: 06/11/2013 21:37
I see it, thanks

You need to be signed in to perform that action.