18a^2-{-6a^2+[5a-4a^2-(a^2-2a)]+15a^2-5a},其中a=-1/6

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18a^2-{-6a^2+[5a-4a^2-(a^2-2a)]+15a^2-5a},其中a=-1/6
18a^2-{-6a^2+[5a-4a^2-(a^2-2a)]+15a^2-5a},其中a=-1/6

18a^2-{-6a^2+[5a-4a^2-(a^2-2a)]+15a^2-5a},其中a=-1/6
18a² - {-6a²+[5a-4a²-(a²-2a)]+15a²-5a}
= 18a² - {-6a²+[5a-4a²-a²+2a]+15a²-5a}
= 18a² - {-6a²+5a-4a²-a²+2a+15a²-5a}
= 18a² - {4a²+2a}
= 18a² - 4a² - 2a
= 14a² - 2a
= 14×(-1/6)² - 2×(-1/6)
= 14×1/36 + 2×1/6
= 7/18 + 1/3
= 13/18

化简得,12a^2+2a
a=-1/6
12a^2+2a=12(-1/6)^2+2(-1/6)=1/3-1/3=0