Fan and medal

Solve using perfect square factoring patterns.

x^2 – 10x + 25 = 9

A.

{–4, 12}

B.

{4, –12}

C.

{–8, –2}

D.

{2, 8}

Question

Fan and medal

Solve using perfect square factoring patterns.

 

        x^2 – 10x + 25 = 9 
 
 
 

 
 

  

  A. 
 
{–4, 12}
   
   

 
 

  

  B. 
 
{4, –12}
   
   

 
 

  

  C. 
 
{–8, –2}
   
   

 
 

  

  D. 
 
{2, 8}

anonymous · Answer

Answer is D. You take 9 away from each side and then factor it our to be (x-8)(x-2). You then take the opposite of the numbers in the parenthesis, 2 and 8.

cruffo · Answer

or note that the left-hand side is a perfect square binomial, and factor.  Then use the square root property to take the square root of both sides:

$x^2 - 10x +25 = 9$
$(x-5)^2 = 9$
$x-5 = 3$ and $x-5 = -3$
$x = 8$ and $x = 2$