作业帮初二数学题求解!绝对给好评!
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初二数学题求解!绝对给好评!
初二数学题求解!绝对给好评!
初二数学题求解!绝对给好评!
D
原式=(-4*0.25)2009+(-0.125*8)2008*0.125
=(-1)2009+(-1)2008*0.125
=(-1)+0.125
=-0.875
ax^2-4ax+4a
=a(x^2-4x+4)
=a(x-2)^2
x²(x-y)+y²(y-x)
=x²(x-y)-y²(x-y)
=(x²-y²)(x-y)
=(x+y)(x-y)(x-y)
=(x+y)(x-y)²
4a²b²-(a²+b²-c²)²
=[2ab+(a²+b²-c²)][2ab-(a²+b²-c²)]
=(2ab+a²+b²-c²)(2ab-a²-b²+c²)
=[(a+b)²-c²][c²-(-2ab+a²+b²)]
=(a+b+c)(a+b-c)[c²-(a-b)²]
=(a+b+c)(a+b-c)[c+(a-b)][c-(a-b)]
=(a+b+c)(a+b-c)(c+a-b)(c-a+b)
原式=2a2+2ab-a2-2ab-b2
=a2-b2
将a=根号2008,b=根号2007代入,得
a2-b2=2008-2007=1
3.D
3.D
4.=1-0.125=0.875
5.a(x²-4x-4)=a(x-2)²
6.=x²(x-y)-y²(x-y）=（x-y）(x²-y²)=（x-y）（x+y）（x-y）
7.
3 D
4
(-4)^2009*(0.25)^2009+(-0.125)^2009 *8^2008
=-4^2009*(1/4)^2009-(1/8)*(1/8)^2008 *8^2008
=-(4*(1/4))^2009-(1/8)*((1/8)*8)^2008
=-1^2009-(1/8)*1^2008
=-1-1/8
=-9/8
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3 D
4
(-4)^2009*(0.25)^2009+(-0.125)^2009 *8^2008
=-4^2009*(1/4)^2009-(1/8)*(1/8)^2008 *8^2008
=-(4*(1/4))^2009-(1/8)*((1/8)*8)^2008
=-1^2009-(1/8)*1^2008
=-1-1/8
=-9/8
5
ax^2-4ax+4a
=a(x^2-4x+4)
=a(x-2)^2
6
x²(x-y)+y²(y-x)
=x²(x-y)-y²(x-y)
=(x²-y²)(x-y)
=(x+y)(x-y)(x-y)
=(x+y)(x-y)²
7
4a²b²-(a²+b²-c²)²
=[2ab+(a²+b²-c²)][2ab-(a²+b²-c²)]
=(2ab+a²+b²-c²)(2ab-a²-b²+c²)
=[(a+b)²-c²][c²-(-2ab+a²+b²)]
=(a+b+c)(a+b-c)[c²-(a-b)²]
=(a+b+c)(a+b-c)[c+(a-b)][c-(a-b)]
=(a+b+c)(a+b-c)(c+a-b)(c-a+b)
8
2a(a+b)-(a+b)²
=[2a-(a+b)](a+b)
=(a-b)(a+b)
=a²-b²
=(√2008)²-(√2007)²
=2008-2007
=1
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