Answer:
(x-7)(x-7)
Explanation:
this is a perfect square 
x^2-14x+49
take the square of the first number, 
X^2 = x times x
the sign of the second number 
-14x= (-)
the square of the last number 
49= 7x7
to check your work you foil it out 
(x-7)(x-7)
x times x = X^2
x times -7= -7x
-7 times x = -7x
-7times -7= 49 
then combine like terms 
x^2-7x-7x+49 = x^2-14x+49