What do you need to add to complete the square for #x^2+8x#?

1 Answer
Apr 1, 2018

Answer:

16

Explanation:

Since the #8x# is positive, the equation #(x+y)^2# must have #y# as a positive number. Let's see this!

An easy way to complete the square if you have the constants for #x^2# and #x# but not the non-variable number is to divide the #x# constant, and then square it. Just like this:

#8x#/#2##=4#.
#4^2=16#.

The last number must be 16. Let's check it.

#(x+4)^2=x^2+8x+color(red)16#

The answer is #16#.

Yay!