Question

When solving x2 - 20x = 5 by completing the square what value is added to both sides of the equation?

-4
4
50
100?

Answer 1

We have
\[x^2-20x=5\]
We need to get the form
\[(x-a)^2=x^2-2ax+a^2\]
here 2a=20
so
a=10
we need to add 100 both sides
\[x^2-20x+100=105\]
so
we get
\[(x-10)^2=105\]