SOLUTION: find the missing root if 7 is a root of x^2+bx-21=0

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Question 702890: find the missing root if 7 is a root of x^2+bx-21=0

Answer by mouk(232) About Me  (Show Source):
You can put this solution on YOUR website!
Using the formula for the product of roots:
+alpha+%2A+beta+=+c%2Fa+
gives:

+7+%2B+beta+=+-21%2F1+
+beta+=+-21+-+7+
+beta+=+-28+