Answer:
Step-by-step explanation:
Key to this method is remembering that

So, if you divide the coefficient of x by 2 and square it, that will complete the square. With that in mind, things are easy.
6/2 = 3, so add 

So, c=9
Similarly, for the other two,

You don't really have to worry about the sign, since squaring will always make it positive

Answer:
Nearest ten thousand: 250,000 Nearest hundred thousand: 200,000
Step-by-step explanation:
For the nearest ten thousand, look at that place which is the 4 then look at the number next to it. Its a 6. That 6 is closer to ten than it is to 0 so you round up to the next number which is 250,000. For the hundred thousand place do the same thing. Look at the number next to it which is 4 which is closer to 0 than 10 so you round down to 200,000.
First find x and y.
Solve system of equations by elimination.
3x-y=3
+(-x+y=3)
---------------
2x=6
x=3
Now plug in x into one of the equations to find y.
-3+y=3
y=6
xy=3x6=18