Fan and Medal

What number should be added to the expression x^2 + 4x to change it into a perfect square trinomial?

A.
2

B.
4

C.
8

D.
1

Question

Fan and Medal

What number should be added to the expression x^2 + 4x to change it into a perfect square trinomial?
  
 
 

 
 

  

  A. 
  2   
   

 
 

  

  B. 
  4   
   

 
 

  

  C. 
  8   
   

 
 

  

  D. 
  1

anonymous · Answer

@SandeepReddy

anonymous · Answer

perfect square trinomial ?

anonymous · Answer

yes

anonymous · Answer

we have the highest power of x as 2 so adding any number can only give us, at it's best. a perfect square binomial !

anonymous · Answer

i think the answer is 4 as
x^2 + 4x + c = 0
we have 
$$(a + b )^2 = a^2 + 2ab + b^2$$
so here a is x and we need to know b so that the number we should add becomes b^2
so 
2ab = 4x
2*x*b = 4x
b = 4x/2x = 2
so that led us to b = 2 so number we should is b^2 = > 2 squared = 4

anonymous · Answer

but that only makes it perfect square binomial not trinomial