请问这题怎么写呀,求解答
2019-03-17 · 知道合伙人教育行家
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▲(2b+a)(-2b-a)-(a+2b)²+8b²
=-(2b+a)²-(a+2b)²+8b²
=8b²-2(a+2b)²
=8*4-2*(1/2 -2*2)²
=32-2*(49/4)
=32-49/2
=7又1/2
▲[1-a/(a+1)] ÷ (a²-1)/(a²+2a+1)
=[1-a/(a+1)]*[(a+1)²/(a+1)(a-1)]
=[1-a/(a-1)]*[(a+1)/(a-1)]
=[1/(a-1)]*[(a+1)/(a-1)]
=(a+1)/(a-1)²
=(√3+2)/3
=-(2b+a)²-(a+2b)²+8b²
=8b²-2(a+2b)²
=8*4-2*(1/2 -2*2)²
=32-2*(49/4)
=32-49/2
=7又1/2
▲[1-a/(a+1)] ÷ (a²-1)/(a²+2a+1)
=[1-a/(a+1)]*[(a+1)²/(a+1)(a-1)]
=[1-a/(a-1)]*[(a+1)/(a-1)]
=[1/(a-1)]*[(a+1)/(a-1)]
=(a+1)/(a-1)²
=(√3+2)/3
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2019-03-17
展开全部
(2b+a)(-2b-a)-(a+2b)²+8b²
=-(2b+a)(2b+a)-(a+2b)²+8b²
=-(2b+a)²-(a+2b)²+8b²
=-2(a+2b)²+8b²
当a=1/2,b=-2时,
-2(a+2b)²+8b²
=-2[1/2+2x(-2)]²+8x(-2)²
=-2[1/2-4]²+8x4
=-2[7/2]²+32
=-49/2+32
=15/2
=-(2b+a)(2b+a)-(a+2b)²+8b²
=-(2b+a)²-(a+2b)²+8b²
=-2(a+2b)²+8b²
当a=1/2,b=-2时,
-2(a+2b)²+8b²
=-2[1/2+2x(-2)]²+8x(-2)²
=-2[1/2-4]²+8x4
=-2[7/2]²+32
=-49/2+32
=15/2
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