七年级数学下册第九章习题答案热门五篇

七年级数学下册第九章的习题你做得怎么样了？对照一下正确答案吧。接下来是读文网小编为大家带来的七年级数学下册第九章习题的答案，供大家参考。

七年级数学下册第九章习题答案：习题9.1

习题9.2第1题答案解：(1)1/2ab2•(2a2b-3ab2)=1/2ab2•(2a2b)+1/2ab2•(-3ab2)=a3b3-3/2a2

(2)x(2x-5)+3x(x+2)-5x(x-1)=2x2-5x+3x2+6x-5x2+5x=6x.

(3)a(a2+ab+b2)-b(a2+ab+b2)=a3+a2b+ab2-a2b-ab2-b3=a3-b3.

(4)原式=a3-3a+a3+3a2-3a3+3a=-a3+6a2.

习题9.2第2题答案解：因为A=-2ab,B=4ab(a-b)=4a2b-4ab2,所以A•B=-2ab(4a2b-4ab2)=-8a3b2+8a2b3.

习题9.2第3题答案(1)-6ab (2)2a (3)2ab 5b2 (4)1 4ab 8a2b2

习题9.2第4题答案解：(a+b)(c+d)=(a+b)•c+(a+b)•d=ac+bc+ad+bd.

七年级数学下册第九章习题答案：习题9.2

习题9.1第1题答案

习题9.1第2题答案

习题9.1第3题答案

七年级数学下册第九章习题答案：习题9.3

习题9.4第1题答案(1)4a2+12ab+9b2

(2)16x2-40xy+25y2

(3)1/3a2-2ab+3b2

(4)a2+4ab+4b2

习题9.4第2题答案解：草坪的面积可表示为S=20×20-20•a-20•a+a2，也可表示为S=(20-a)(20-a).得到等式(20-a)2=400-40a+a2.说明：草坪的面积S=20×20-20•a-20•a+a2=400-40a+a2.

习题9.4第3题答案

习题9.4第4题答案(1)4m2-9n2 (2)4a2-25b2 (3)4-9x2 (4)y2-1/9x2

习题9.4第5题答案解：(1)9982=(1000-2) 2=10002-2×1000×2+22=1000000-4000+4=996004.

(2)1007×993=(1000+7)(1000-7)=10002-72=1000000-49=999951.

习题9.4第6题答案解：(1)(x-y) 2-x2-2xy+y2-(x2+2xy+y2)-(x2+2xy+y2)=-4xy.

(2)(3a-b) 2+(b+3a) 2=9a2-6ab+b2+b2+6ab+9a2=18a2+2b2.

(5)4(a+2) 2-7(a+3)(a-3)+3(a-1) 2=4(a2+4a+4)-7(a2-9)+3(a2-2a+1)=4a2+16a+169-7a2+63+3a2-6a+3=10a+82.

(6)(2a-b-3)(2a+b+3)=[(2a-3)-b][(2a-3)+b]=(2a-3) 2-b2=4a2-12a+9-b2.

习题9.4第7题答案解：(1)原式=24y+18，当y=0.4时，原式=27.6.

(2)原式=5ab，当a=7/15，b=3/14时，原式=1/2 .

七年级数学下册第九章习题答案：习题9.4

习题9.3第1题答案解(1)(x-3)(2x+5)=2x2+5x-6x-15=2x2-x-15.

(2)(2a+1)(-a-2)=-2a2-4a-a-2=-2a2-5a-2.

(3)(x+1/2)(x-1/3)=x2-1/3x+1/2x-1/6=x2+1/6x-1/6.

(5)(xy+1)(xy-4)=x2y2-4xy+xy-4=x2y2-3xy-4.

(6)(5m-4n)(4m-5n)=20m2-25mn-16mn+20n2=20m2-41mn+20n2.

习题9.3第2题答案解：(1)(2a-b)(a+2b-3)=2a2+4ab-6a-ab-2b2+3b=2a2+3ab-6a+3b-2b2;

(2)(x+y+5)(x+y+4)=[(x+y)+5][(x+y)+4]=(x+y)2+9(x+y)+20=x2+xy+xy+y2+9x+9y+20=x2+2xy+9x+9y+y2+20.

习题9.3第3题答案解：(x-1)(2x+1)-2(x-5)(x+2)=2x2-x-1-2(x2-3x-10)=2x2-x-1-2x2+6x+20=5x+19.当x=1/5时，5x+19=5×1/5+19=20.

习题9.3第4题答案解：(90+a)(60+a)-90×60=90×60+90a+60a+a2-90×60=(a2+150a)(cm2).

答：它的面积将增加(a2+150a)cm2.

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七年级数学下册第九章习题答案：习题9.5

习题9.5第1题答案解：(1)ap-aq+am=a(p-q+m).

(2)4x2-8xy+2x=2x(2x-4y+1).

(3)12xyz-9x2y=3xy(4z-3x).

(5)6a2b-9ab2+15ab=3ab(2a-3b+5).

习题9.5第2题答案解：(1)4ab(2x-y)+b(2x-y)=b(2x-y)(4a+1);

(2)6a(1-b) 2-2(b-1) 2=2(b-1) 2•(3a-1).

习题9.5第3题答案解：(1)1-16a2=(1+4a)(1-4a);

(2)m2-9n2=(m+3n)(m-3n);

(3)4x2-81y2=(2x) 2-(9y2)=(2x+9y)(2x-9y);

(4)9a2x2-b2y2=(3ax+by)(3ax-by).

习题9.5第4题答案解：(1)(x+5) 2-4=(x+5) 2-22=(x+5+2)(x+5-2)=(x+7)(x+3);

(2)(a+b) 2-a2=(a+b+a)(a+b-a)=b(2a+b);

(3)(a2+b2)2-a2b2=(a2b2+ab)(a2b2-ab);

(4)49(a-b)2-16(a+b)2

=[7(a-b)] 2-[4(a+b)] 2

=[7(a-b)+4(a+b)][7(a-b)-4(a-b)]

=(7a-7b+4a+4b)(7a-7b-4a-4b)

=(11a-3b)(3a-11b).

习题9.5第5题答案解：(1)a2b2-2ab+1=(ab-1)2;

(2)9-12a+4a2=(2a-3)2;

(3)4x2+4x+1=(2x+1)2;

(4)x2-6xy+9y2=(x-3y)2.

习题9.5第6题答案解：(1)(a+b)2+6(a+b)+9=(a+b+3)2;

(2)16-24(x-y)+9(x-y)2=[3(x-y)-4]2=(3x-3y-4)2;

(3)a2-2a(b+c)+(b+c)2=[a-(b+c)]2=(a-b-c)2;

(4)4x2-4x(y-1)+(y-1)2=[2x-(y-1)]2=(2x-y+1) 2.

习题9.5第7题答案解：(1)-a+2a2-a3=-a(1-2a-22)=-a(a-1)2;

(2)3ax2-3ay2=3a(x2-y2)=2a(x+y)(x-y);

(3)16a2b-13a2-4ab2=-4a(4a2-4ab+b2)=-4a(2a-b) 2;

(4)x2(y2-1)+(1-y2)=(y2-1)(x2-1)=(y+1)(y-1)(x+1)(x-1).

习题9.5第8题答案