Answer:
Step-by-step explanation:
Using brackets will really help.
y = (x^2 + 4x + ... ) - 5 You are trying to complete the square. The square in this case is a trinomial that is squared.
To do that, you take 1/2 the linear term (4x)/2, drop the x (4/2), and square the result (4/2)^2. The number is 2^2 which is 4.
So far what you have is
y = (x^2 + 4x + 4) - 5
Now you just can't add 4 without adjusting it somehow. If you do, the whole question will change it's value. Because you added 4 inside the brackets, you must subtract 4 outside the brackets.
What that means is 4 inside - 4 outside. So it looks like this
y = (x^2 + 4x + 4) - 5 - 4
Now you continue on
y = (x + 2)^2 - 9 The 4 combines with the 5 to make nine.
