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Question Number 164135 by mathlove last updated on 14/Jan/22

p(x)+xp(−x)=x^2 +1  faind   p(2)=?

$${p}\left({x}\right)+{xp}\left(−{x}\right)={x}^{\mathrm{2}} +\mathrm{1} \\ $$$${faind}\:\:\:{p}\left(\mathrm{2}\right)=? \\ $$

Answered by mr W last updated on 14/Jan/22

p(x)+xp(−x)=x^2 +1   ...(i)  p(−x)−xp(x)=x^2 +1  xp(−x)−x^2 p(x)=(x^2 +1)x   ...(ii)  (i)−(ii):  (1+x^2 )p(x)=(x^2 +1)(1−x)  ⇒p(x)=1−x  ⇒p(2)=1−2=−1

$${p}\left({x}\right)+{xp}\left(−{x}\right)={x}^{\mathrm{2}} +\mathrm{1}\:\:\:...\left({i}\right) \\ $$$${p}\left(−{x}\right)−{xp}\left({x}\right)={x}^{\mathrm{2}} +\mathrm{1} \\ $$$${xp}\left(−{x}\right)−{x}^{\mathrm{2}} {p}\left({x}\right)=\left({x}^{\mathrm{2}} +\mathrm{1}\right){x}\:\:\:...\left({ii}\right) \\ $$$$\left({i}\right)−\left({ii}\right): \\ $$$$\left(\mathrm{1}+{x}^{\mathrm{2}} \right){p}\left({x}\right)=\left({x}^{\mathrm{2}} +\mathrm{1}\right)\left(\mathrm{1}−{x}\right) \\ $$$$\Rightarrow{p}\left({x}\right)=\mathrm{1}−{x} \\ $$$$\Rightarrow{p}\left(\mathrm{2}\right)=\mathrm{1}−\mathrm{2}=−\mathrm{1} \\ $$

Commented by mathlove last updated on 14/Jan/22

thanks   thear mr W

$${thanks}\:\:\:{thear}\:{mr}\:{W} \\ $$$$ \\ $$

Commented by mathlove last updated on 14/Jan/22

Commented by mr W last updated on 14/Jan/22

look above again!

$${look}\:{above}\:{again}! \\ $$

Commented by mathlove last updated on 14/Jan/22

thank   I know

$${thank}\:\:\:{I}\:{know} \\ $$

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