(а+2)(a-3)-(a+4)(a-7)=(a²-3a+2a-6)-(a²-7a+4a-28)=a²-3a+2a-6-a²+7a-4a+28=2a+22
При а=-1/2
2×(-1/2)+22=-1+22=21
Ответ:21
0.66/1.2=0.55
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1 + 3 + 9 + 27 = (1 + 9) + (3 + 27) = 10 + 30 = 40
<span>1)6а²-6а=6a(a-1)</span><span>
2)5х³-5ху²=5x(x-y)(x+y)
3)8²в²-72а²с²=64в</span>²-72а²с²<span>
4)2а³+3а²-2ав+3в=a</span>²(2a+3)-в(2а-3)