00:01
So the key to this problem is being able to complete the square.
00:04
And what you'll also notice is that x squared is by itself.
00:11
That's y squared plus 36y minus 72 is equal to zero.
00:21
So what i would do is because every teacher is a little different is i would first add 72 to the right side and i would factor out of negative nine from both the y squared and the 36 and you can double check that this is equal if i were to distribute that negative 9 in there would equal what's right there and then i leave a space right here because i'm going to complete the square which is taking half of this number negative 4 squared is equal to positive 4 so that's what i'm going to add right here but i'm not really adding 4 to the problem i am subtracting negative 9 times, well, i guess i say adding negative 9 times 4 would be 36.
01:09
So if i remove 36 from the left side, i also have to remove 36 from the right side.
01:15
So as i'm looking at that problem, 702 minus 36 is 36.
01:20
And what i have on the left side is 9 times a perfect square trinomial.
01:25
So it's y minus 2 squared.
01:28
I'm almost there.
01:30
What i need to do is get this equation equal to 36, which i can do by dividing every piece by 36.
01:38
And it might even help you to rewrite this as x minus zero squared over six squared.
01:44
And then nine goes into 36 four times, but i'm going to write it as two squared.
01:49
And you can double check that this math is correct...