第1个回答 2013-01-05
解:16-49m²=(4+7m)(4-7m)
-1/4xy³+0.09xy=-xy(1/4y²-0.09)=-xy(1/2x-0.3)(1/2x+0.3)
-1+16x²=16x²-1=(4x+1)(4x-1)
6.4²-3.6² =(6.4+3.6)(6.4-3.6)=10×2.8=28
1.4²×9-2.3²×36 =9[(1.4)²-2.3²×4]=9[1.4+2.3×2][1.4-2.3×2]=9×6×(-3.2)=-172.8
xy-9x³y=xy(1-9x²)=xy(1+3x)(1-3x)
a³[x+y]²-4a³c²=a³[(x+y)²-4c²]=a³[(x+y)+2c][(x+y)-2c]=a³(x+y+2c)(x+y-2c)
4[a-b]²-[a+b]²=[2(a-b)+(a+b)][[2(a-b)-(a+b)]=(3a-b)(a-3b)
第2个回答 2013-01-05
1.(4-7m)*(4+7m)
2.-xy[0.25y^2-0.09]=-xy(0.5y-0.3)(0.5y+0.3)
3.(4x+1)(4x-1)
4.a^2b(b+2)(b-2)
5.原式=(6.4+3.6)(6.4-3.6)=10*2.8=28
原式=(1.4*3-2.3*6)(1.4*3+2.3*6)=-9.6*18=-172.8
6.xy(1-3x^2)(1+3x^2)
7.a^3(x+y-2c)(x+y+2c)
8.(x-y)(2a-b)(2a+b)
9.(a-3b)(3a-b)
第3个回答 2013-01-05
1、(7+4m)(7-4m)
2、(四分之y方+0.3)(四分之y方-0.3)
3、(4x+1)(4x-1)
4、a²b(b+2)(b-2),
1.4²×9-2.3²×36 :化成平方的形式(1.4×3)²-(2.3×6)²=(1.4×3+2.3×6)(1.4×3-2.3×6)
5、xy-9x^3y=xy(1-y^2)=xy(1+y)(1-y)
6、a^3[x+y]²-4a^3c² =a^3([x+y]²-4c²)=a^3(x+y+2c)(x+y-2c)
7、4a²[x-y]+b²[y-x] =[x-y](4a²-b²)=[x-y](2a+b)(2a-b)
8、4[a-b]²-[a+b]²=[2(a-b)]²-[a+b]²=(3a-b)(a-3b)