document.write( "Question 760085: How do I find the missing A value in a quadratic equation? \n" ); document.write( "

Algebra.Com's Answer #462420 by KMST(5328) $\"\"$ $\"About$

You can put this solution on YOUR website!
I'm hoping this answers your question.
\n" ); document.write( " $\"ax%5E2%2Bbx%2Bc=0\"$ is one of infinite equivalent equations, and you may not need to find $\"a\"$ .
\n" ); document.write( "If you know that the solutions of a quadratic equation are $\"x=c\"$ and $\"x=d\"$ , you can conclude that one of the equivalent equations with those solutions is
\n" ); document.write( " $\"%28x-c%29%28x-d%29=0\"$ which can also be written as $\"x%5E2-%28c%2Bd%29x%2Bcd=0\"$
\n" ); document.write( "If you multiply both sides of the equal sign times a non-zero number, you get an equivalent equation, such as
\n" ); document.write( " $\"2x%5E2-2%28c%2Bd%29x%2B2cd=0\"$ if you multiply times $\"2\"$ , or
\n" ); document.write( " $\"ax%5E2-a%28c%2Bd%29x%2Bacd=0\"$ if you multiply times a number $\"a\"$ such that $\"a%3C%3E0\"$ .
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\n" ); document.write( "On the other hand, If you are looking for a quadratic function
\n" ); document.write( " $\"y=ax%5E2%2Bbx%2Bc\"$ , you need at least 3 (x,y) points (or equivalent information) to find $\"a\"$ , $\"b\"$ , and $\"c\"$ .
\n" ); document.write( "The coordinates of the vertex and one other point would do too. \n" ); document.write( "

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