Wednesday, July 21, 2010

Q12

Given that m2+m+1, m2+2m+11,and m2+3m+28 form three consecutive terms of a geometric sequence.find m


m2+3m+28 = m2+2m+11

m2+2m+11 m2+m+1

(m2+3m+28)( m2+m+1)= (m2+2m+11)2

m4+m3+m2+3m3+3m2+3m+28m2+28m+28=m4+2m3+11m2+2m3+4m2+22m+11m2+22m+121

m4-m4+m3+3m2-2m3+m2+28m2-11m2-4m2-11m2+3m+28m-22m+28-121=0

6m2-13m-93=0

m=31/6

m=-3



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