先化简在求值(a-2b)(a²+2ab+4b²)-a(a-5b)(a+3b),其中a=-1,b=2
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先化简在求值(a-2b)(a²+2ab+4b²)-a(a-5b)(a+3b),其中a=-1,b=2
先化简在求值(a-2b)(a²+2ab+4b²)-a(a-5b)(a+3b),其中a=-1,b=2
先化简在求值(a-2b)(a²+2ab+4b²)-a(a-5b)(a+3b),其中a=-1,b=2
(a-2b)(a²+2ab+4b²)-a(a-5b)(a+3b)
=(a-2b)(a²+2ab+4b²)-a(a²-2ab-15b²)
=a³+2a²b+4ab²-2a²b-4ab²-8b³-a³+2a²b+15ab²
=2a²b+15ab²-8b³
=2×(-1)²×2+15×(-1)×2²-8×2³
=4-60-64
=-120