Algebra 2
posted by Anonymous on .
Complete the square and write in graphing form.
2x^2=5x+12

2 x ^ 2 = 5 x + 12
Subtract 5 x + 12 to both sides
2 x ^ 2  ( 5 x + 12 ) = 5 x + 12  ( 5 x + 12 )
2 x ^ 2  5 x  12 = 0 Divide both sides by leading coefficient ( 2 )
x ^ 2  5 x / 2  6 = 0 Add 6 to both sides
x ^ 2  5 x / 2  6 + 6 = 0 + 6
x ^ 2  5 x / 2 = 6
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Take one half of the coefficient of x and square it.
In this case [ ( 5 / 2 ) / 2 ] ^ 2 = ( 5 / 4 ) ^ 2 = 25 / 16
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Add 25 / 16 to both sides
x ^ 2  5 x / 2 + 25 / 16 = 6 + 25 / 16
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Remark :
x ^ 2  5 x / 2 + 25 / 16 = ( x  5 / 4 ) ^ 2
6 = 96 / 16
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( x  5 / 4 ) ^ 2 = 96 / 16 + 25 / 16
( x  5 / 4 ) ^ 2 = 121 / 16
x  5 / 4 = + OR  sqrt ( 121 / 16 )
x  5 / 4 = + OR  11 / 4 Add 5 / 4 to both sides
x  5 / 4 + 5 / 4 = + OR  11 / 4 + 5 / 4
x = + OR  11 / 4 + 5 / 4
x1 = 11 / 4 + 5 / 4 = 16 / 4 = 4
x2 =  11 / 4 + 5 / 4 =  6 / 4 =  3 / 2
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2 x ^ 2 = 5 x + 12
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