+0  
 
+1
138
3
avatar+50 

Find the factors ? x^2-2x-3 ??

TandCforlife  Mar 27, 2017
Sort: 

3+0 Answers

 #1
avatar+26265 
+1

x2 - 2x - 3 → (x - 3)(x + 1)

.

Alan  Mar 27, 2017
 #2
avatar+50 
+1

Thx so much do u know these by any chance ? 

 

x^2+2x-8    x^2+x-8     x^2-4 ???    Pls ?

TandCforlife  Mar 27, 2017
edited by TandCforlife  Mar 27, 2017
 #3
avatar+26265 
+1

Think of these as (x - a)(x - b) → x2 - (a+b)x +a*b

 

(1) Compare with  x2 + 2x - 8  

 

We must have a*b = -8  so what are the possible products:

-8  and 1 

8 and -1 

-4 and 2

4 and -2

 

We must also have -(a + b) = 2 so, using the above possible products:

-8 and 1  give -(-8 + 1) → 7  no!

8 and 1 give -(8 + 1) → -9 no!

-4 and 2 give -(-4 + 2) → 2  yes!

4 and -2 give -(4 - 2) → -2 no!

 

So we have x2 + 2x - 8 → (x - -4)(x - 2) → (x + 4)(x - 2)

.

Try this yourself with x2 - 4

 

x2 + x - 8 doesn't have nice integer roots.  You can do this using the quadratic formula, for example.

.

Alan  Mar 27, 2017

15 Online Users

avatar
avatar
We use cookies to personalise content and ads, to provide social media features and to analyse our traffic. We also share information about your use of our site with our social media, advertising and analytics partners.  See details