document.write( "Question 66047: When working out the rule for a quadratic equation (ax^2+bx+c)from a tables of different values how do you find B? I know that a=half second difference pattern and c=y when x=0. I covered it ages ago and its just gone straight out of my head lol.. Thanks Jocelyn \n" ); document.write( "

Algebra.Com's Answer #46776 by checkley71(8403) $\"\"$ $\"About$

You can put this solution on YOUR website!
$\"x+=+%28-b+%2B-+sqrt%28+b%5E2-4%2Aa%2Ac+%29%29%2F%282%2Aa%29+\"$
\n" ); document.write( "This is the quadratic equation. However i think you are asking how to find the middle term of the equation ax^2+bx+c=0
\n" ); document.write( "It generally is best to set a=1 by dividing all terms by a. Then set up the following table assuming we have the equation (x^2-10x+25).
\n" ); document.write( "Knowing that x+y=b & x*y=c we need to find:
\n" ); document.write( "The factors of (c) 25. They are (+1)(+25),(-1)(-25) & (+5)(+5),(-5)(-5)
\n" ); document.write( "Now find 2 of these factors that add up to (b) (-10). That would be
\n" ); document.write( "(-5)+(-5)=-10
\n" ); document.write( "So the factors of x^2-10x+25 are (x-5)(x-5).[-5-5=-10 & (-5)(-5)=25]
\n" ); document.write( "Another example is x^2-3x-10.
\n" ); document.write( "The factors of (c) -10 are (-1)(10),(1-10),(-2)(5),(2)(-5).
\n" ); document.write( "Now find 2 of these factors that add up to (b) (-3). That would be (2)+(-5)=-3.
\n" ); document.write( "So the factors here would be (x+2)(x-5). [2-5=-3 & (2)(-5)=-10]
\n" ); document.write( "Hope this helps.
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