Question

In order to complete the square for the equation below, what value should be added to both sides of the equation?

x2 - 8x + ? = 42 + ?

Answer 1

? = 16

Explanation:

x2 - 8x + ? = 42 + ?

1. Take the coefficient of the middle term 8x, which is 8 and divide it by 2.
`(8)/(2) = -4`. Then square it
`-4^(2) = 16`

2. Take 16 and add it to both sides:
`x^2 - 8x + 16 = 42 + 16`

2. Take half of the coefficient 8 that you divided by 2, which is 4 and insert 4 into the equation
`(x -4)^2 = 58`

3. ? = 16