题目内容
化简求值:2(3a2-5b)-[-3(a2-3b)],其中a=
,b=-2.
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2(3a2-5b)-[-3(a2-3b)],
=6a2-10b+3(a2-3b),
=6a2-10b+3a2-9b,
=9a2-19b,
当a=
,b=-2时,原式=9×(
)2-19×(-2)=39.
=6a2-10b+3(a2-3b),
=6a2-10b+3a2-9b,
=9a2-19b,
当a=
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| 3 |
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| 3 |
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