SOLUTION: In one root ax^2+bX+c=0 is double the other.,prove that 2b^2=9ac ??????

SOLUTION: In one root ax^2+bX+c=0 is double the other.,prove that 2b^2=9ac ??????

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Question 818245: In one root ax^2+bX+c=0 is double the other.,prove that 2b^2=9ac ??????
Answer by KMST(5328) (Show Source): You can put this solution on YOUR website!
The solutions to are ,
which I will temporarily abbreviate as
with .

If ,

which squares into .

If ,

which squares into .

Either way which means .
So , and adding to both sides we get
, which dividing both sides by 4 gives us
or .
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