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Slide 2

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Why is it called that???
· It is called `Completing the Square' because of
the method where you:
1) write down a squared bracket, and then
2) put a number on the end to `Complete' it.
X2 + 12x ­ 5 = (x +6)2 - 41
completed
The square…read more

Slide 3

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The Method (I hope you're paying attention, this bit is important)
x2 + 8x + 7 = 0
· First check the quadratic equation* all equals
to 0. In this case it is.
· Then half the coefficient* of x. 8 ÷ 2 = 4
· This is the number that goes inside the
squared bracket. Thus (x + 4)2
* (check the last slide if you don't know what it means)…read more

Slide 4

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x2 + 8x + 7 = 0
Expand.....
· Then expand the brackets,
(x + 4)2
and you should get.....
x2 + 8x + 16 = 0
· But we haven't got a +16 in our quadratic
equation so.....…read more

Slide 5

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x2 + 8x + 7 = 0
Take away and add....
· We then take away 16 and add 7 from the
quadratic equation.
(x + 4)2 ­ 16 +7 = 0
· When we simplify this we get:
(x + 4)2 ­ 9 = 0…read more

Slide 6

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Find the value of x...
· Finally we must find the value of x by
rearranging the equation (x + 4)2 ­ 9 = 0 :
2 + 9 on both
(x + 4) = 9 sides
Square route both sides, to
give 3 or -3. because 3x3=9
x + 4 = 3 or -3 and -3x-3=9
Then take away 4
x = -1 or -7 from both sides to
give -1 or -7…read more

Slide 7

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Preview of page 7

Comments

daviesg

A great demonstration of completing the square method to solve a quadratic equation

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