Problem Solving - 30

Which of the following is always equal to sqrt (9 + x^2 - 6x)?

a) x - 3
b) 3 + x
c)|3 - x|
d)|3 + x|
e) 3 - x

Answer: C

sqrt (9+x^2-6x)
= sqrt( (3-x)^2 )
= |3-x|