Find the value of p so that the equation x^2+10x+21=0 and x^2+9x+p=0 may have a common root. Find also the equation formed by the other root.
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Observe that . Hence roots of are and .
Observe that roots of are given by .
Thus if you find the values of where or you're done.
Sorry. This can be done easier ;p.
Since you must find p such that . Observe the only possibility is .
Thus now we must find p such that: . This gives
Now you can do the same trick for to find another value of p
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