Answer:
x = 4 twice.
Explanation:
x^2-8x+ 16=0
Bring the constant to the other side.
x^2-8x=-16
Half the coefficient of x and square the result. Add to both sides.
x^2-8x+[-8/2]^2=-16+(-8/2)^2
x^2-8x+16= 16-16
x^2-8x+16=0
Now, whenever there's a perfect square constant, take the root of that constant. Since the coeff. of x is negative (-8),
(x-4)(x-4)=0 [-4^2=16 and -4+(-4)=-8]
Therefore, x-4=0 twice.
x=4 twice.
Hope this helps! :]