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Question Number 125511 by sandy_delta last updated on 11/Dec/20
if :  f(x)=f(−x) for x∈R  ∫_(−3) ^3  f(x) dx = 0  ∫_(−2) ^3  f(x) dx = 5  then ∫_0 ^2  f(x) dx = ?
$$\mathrm{if}\:: \\ $$$$\mathrm{f}\left(\mathrm{x}\right)=\mathrm{f}\left(−\mathrm{x}\right)\:\mathrm{for}\:\mathrm{x}\in\mathbb{R} \\ $$$$\underset{−\mathrm{3}} {\overset{\mathrm{3}} {\int}}\:\mathrm{f}\left(\mathrm{x}\right)\:\mathrm{dx}\:=\:\mathrm{0} \\ $$$$\underset{−\mathrm{2}} {\overset{\mathrm{3}} {\int}}\:\mathrm{f}\left(\mathrm{x}\right)\:\mathrm{dx}\:=\:\mathrm{5} \\ $$$$\mathrm{then}\:\underset{\mathrm{0}} {\overset{\mathrm{2}} {\int}}\:\mathrm{f}\left(\mathrm{x}\right)\:\mathrm{dx}\:=\:? \\ $$
Commented by liberty last updated on 11/Dec/20
⇒∫_(−3) ^3 f(x)dx=2∫_0 ^3 f(x)dx=0 ; ∫_0 ^3 f(x)dx=0  ∫_(−2) ^3 f(x)dx=∫_(−2) ^0 f(x)dx+∫_0 ^3 f(x)dx              5      = ∫_0 ^2 f(x)dx+0             5      = ∫_0 ^2  f(x)dx
$$\Rightarrow\underset{−\mathrm{3}} {\overset{\mathrm{3}} {\int}}{f}\left({x}\right){dx}=\mathrm{2}\underset{\mathrm{0}} {\overset{\mathrm{3}} {\int}}{f}\left({x}\right){dx}=\mathrm{0}\:;\:\underset{\mathrm{0}} {\overset{\mathrm{3}} {\int}}{f}\left({x}\right){dx}=\mathrm{0} \\ $$$$\underset{−\mathrm{2}} {\overset{\mathrm{3}} {\int}}{f}\left({x}\right){dx}=\underset{−\mathrm{2}} {\overset{\mathrm{0}} {\int}}{f}\left({x}\right){dx}+\underset{\mathrm{0}} {\overset{\mathrm{3}} {\int}}{f}\left({x}\right){dx}\: \\ $$$$\:\:\:\:\:\:\:\:\:\:\:\mathrm{5}\:\:\:\:\:\:=\:\underset{\mathrm{0}} {\overset{\mathrm{2}} {\int}}{f}\left({x}\right){dx}+\mathrm{0} \\ $$$$\:\:\:\:\:\:\:\:\:\:\:\mathrm{5}\:\:\:\:\:\:=\:\underset{\mathrm{0}} {\overset{\mathrm{2}} {\int}}\:{f}\left({x}\right){dx} \\ $$
Commented by sandy_delta last updated on 12/Dec/20
thank you
$$\mathrm{thank}\:\mathrm{you} \\ $$

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