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January 29, 2015

January 29, 2015

Posted by **Anne** on Thursday, December 8, 2011 at 12:50am.

f(x)=2x^2-20x-3

- urgent math -
**Anonymous**, Thursday, December 8, 2011 at 10:04am2 x ^ 2 - 20 x - 3

2 ( x ^ 2 - 10 x - 3 / 2 )

2 ( x ^ 2 - 10 x + ? - 3 / 2 ) + ?

The quantity to add is "the square of: (1/2) times the coefficient of the middle term -10"

That is:

[ ( 1 / 2 ) * ( - 10 ) ] ^ 2

( - 5 ) ^ 2

2 ( x ^ 2 - 10 x - 3 / 2 )=

2 [ x ^ 2 - 10 x + ( - 5 ) ^ 2 - 3 / 2 ) - ( - 5 ) ^ 2 ]

2 [ x ^ 2 - 10 x + ( - 5 ) ^ 2 ] - 2 * 3 / 2 - 2 * 25

x ^ 2 - 10 x + ( - 5 ) ^ 2 = ( x - 5 ) ^ 2

2 * 3 / 2 = 3

2 * 25 = 50

2 [ x ^ 2 - 10 x + ( - 5 ) ^ 2 - 3 / 2 ) - ( - 5 ) ^ 2 ] =

2 ( x - 5 ) ^ 2 - 3 - 50 =

2 ( x - 5 ) ^ 2 - 53

2 x ^ 2 - 20 x - 3 = 2 ( x - 5 ) ^ 2 - 53

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