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Given-a-rational-function-f-x-ax-2-bx-c-x-q-has-minimum-point-at-2-9-and-maximum-point-at-2-1-Find-value-of-a-b-c-and-q-




Question Number 156188 by naka3546 last updated on 09/Oct/21
Given  a  rational  function       f(x) =  ((ax^2 +bx+c)/(x+q))  has  minimum  point  at (−2,9)  and  maximum  point  at  (2,1) .  Find  value  of  a, b, c,  and  q .
$${Given}\:\:{a}\:\:{rational}\:\:{function} \\ $$$$\:\:\:\:\:{f}\left({x}\right)\:=\:\:\frac{{ax}^{\mathrm{2}} +{bx}+{c}}{{x}+{q}} \\ $$$${has}\:\:{minimum}\:\:{point}\:\:{at}\:\left(−\mathrm{2},\mathrm{9}\right)\:\:{and}\:\:{maximum}\:\:{point}\:\:{at}\:\:\left(\mathrm{2},\mathrm{1}\right)\:. \\ $$$${Find}\:\:{value}\:\:{of}\:\:{a},\:{b},\:{c},\:\:{and}\:\:{q}\:. \\ $$
Commented by MJS_new last updated on 09/Oct/21
we have 4 unknowns and need 4 equations  (1) f(−2)=9  (2) f(2)=1  (3) f′(−2)=0  (4) f′(2)=0  solve this to get  a=−1  b=5  c=−4  q=0
$$\mathrm{we}\:\mathrm{have}\:\mathrm{4}\:\mathrm{unknowns}\:\mathrm{and}\:\mathrm{need}\:\mathrm{4}\:\mathrm{equations} \\ $$$$\left(\mathrm{1}\right)\:{f}\left(−\mathrm{2}\right)=\mathrm{9} \\ $$$$\left(\mathrm{2}\right)\:{f}\left(\mathrm{2}\right)=\mathrm{1} \\ $$$$\left(\mathrm{3}\right)\:{f}'\left(−\mathrm{2}\right)=\mathrm{0} \\ $$$$\left(\mathrm{4}\right)\:{f}'\left(\mathrm{2}\right)=\mathrm{0} \\ $$$$\mathrm{solve}\:\mathrm{this}\:\mathrm{to}\:\mathrm{get} \\ $$$${a}=−\mathrm{1} \\ $$$${b}=\mathrm{5} \\ $$$${c}=−\mathrm{4} \\ $$$${q}=\mathrm{0} \\ $$
Commented by naka3546 last updated on 09/Oct/21
Thank  you, sir.
$${Thank}\:\:{you},\:{sir}. \\ $$

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