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Question Number 210013 by otchereabdullai@gmail.com last updated on 28/Jul/24

 If f(x)= x^2 +ax+b. if f(1)= 3 and    and one of the roots of the eqiation   f(x)= 0 doubles the other, find the   positive values of a and b.

Iff(x)=x2+ax+b.iff(1)=3andandoneoftherootsoftheeqiationf(x)=0doublestheother,findthepositivevaluesofaandb.

Answered by mr W last updated on 28/Jul/24

say the one root is p, then the other  root is 2p.  p+2p=−a ⇒p=−(a/3)  p×2p=b ⇒2a^2 =9b  f(1)=1^2 +a+b=3 ⇒a+b=2  2a^2 =9(2−a)  ⇒2a^2 +9a−18=0  ⇒a= (3/2), −6 (rejected)  ⇒b=(1/2)

saytheonerootisp,thentheotherrootis2p.p+2p=ap=a3p×2p=b2a2=9bf(1)=12+a+b=3a+b=22a2=9(2a)2a2+9a18=0a=32,6(rejected)b=12

Commented by otchereabdullai@gmail.com last updated on 28/Jul/24

thanks soo much Prof W

thankssoomuchProfW

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