You "complete the square" by adding what is missing to make a square... then subtracting it again.
If you add a and subtract a to an equation, you have not changed the equation's value, becasue you will have added (a - a) = 0. You can add zero as much as you want.
In the case of x^2 -2x, you are looking for a value that will create a square of the form (x-m)^2 = x^2 - 2x + a.
(the sign is minus because of the -2x).
The clue is usually that the middle coefficient (in this case 2) must be twice the product of m and the coefficient of x inside the bracket (in this case, that is 1).
so 2 times (m*1) = 2, gives us that m=1.
(x-1)^2 = x^2 -2x +1
so, our a is 1
We can add 1 (and subtract 1).
x^2 -2x
x^2 -2x + 1 - 1
(x-1)^2 -1
The second problem is the same (except it is using a letter y instead of x).
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If this is homework for a course where you are just beginning to solve such problems, then it is sufficient, for this problem, to say that
you complete the square by adding 1
(and then show how adding 1 makes it a square)
2007-09-28 06:09:41
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answer #1
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answered by Raymond 7
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You "complete the square" by adding what is missing to make a square... then subtracting it again.
If you add a and subtract a to an equation, you have not changed the equation's value, becasue you will have added (a - a) = 0. You can add zero as much as you want.
In the case of x^2 -2x, you are looking for a value that will create a square of the form (x-m)^2 = x^2 - 2x + a.
(the sign is minus because of the -2x).
The clue is usually that the middle coefficient (in this case 2) must be twice the product of m and the coefficient of x inside the bracket (in this case, that is 1).
so 2 times (m*1) = 2, gives us that m=1.
(x-1)^2 = x^2 -2x +1
so, our a is 1
We can add 1 (and subtract 1).
x^2 -2x
x^2 -2x + 1 - 1
(x-1)^2 -1
The second problem is the same (except it is using a letter y instead of x).
2007-09-28 06:01:30
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answer #2
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answered by Anonymous
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How about add 1.
x^2 -2x +1 = (x-1)^2
or
y^2 -2y +1 = (y-1)^2
I think this will work! Hope this helps.
2007-09-28 06:03:46
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answer #3
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answered by pyz01 7
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