Answer:
D. x=4 only
Explanation:
You can solve using the quadratic equation which is
where in this case a=1, b=-8, and c=16. But there is any easier way to solve the equation. You can solve by completing the square which consists of moving the constant to the right side and then adding
. To both sides that way you can rewrite the left side as a perfect square binomial. This is because
will expand to
. So when you add
to both equations. You're able to rewrite the left side as
. Because once you expand it out, it becomes
. Which simplifies to
which is the original equation. In this case there is no need to move the constant, which in this case is 16, to the other side. Since if you calculate the value of (-8/2)^2 it's equal to 16! So this can already be written as a perfect square binomial.
So the equation becomes
Plug values in
Simplify
Take the square root of both sides
Add 4 to both sides