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沪科版七年级上册数学书习题2.2答案

1习题2.2第1题答案

(1)原式=-3x

(2)原式=ab

(3)原式=(2x2-x2)+(x-x)=x2

(4)原式=(3x2-2x2)+(4x-6x)+(-6+5)=x2-2x-1

2习题2.2第2题答案

(1)原式=(2x2+x2)+ (-3x+4x) -2=3x2+x-2

当x=-1/2时,原式=3×(-1/2)2 -1/2-2=-7/4

(2)原式=(7a2+a2)+(-2ab+3ab)+(b2-2b2)=8a2+ab-b2

当a=-2,b=2时,原式= 8×(-2)2+(-2)×2-22=24

3习题2.2第3题答案

(1)按x的降幂排列为-2x3-4x2+13x-6;按x的升幂排列为-6+13x-4x2-2x3

(2)按x的降幂排列为-3x3+3x2y-3xy2+y3; 按x的升幂排列为y3-3xy2+3x2y-x3

4习题2.2第4题答案

(1)原式=3a-b+5a-3b+3

=(3a+5a)+(-b-3b)+3

=8a-4b+3  

(2)原式=2b-3a-2a+3b-1

=(-3a-2a)+(2b+3b)-1

=-5a+5b-1.

(3)原式=4x2+2x2-2y2-3x2-3y2

=(4x2+2x2-3x2)+(-2y2-3y2

=3x2-5y2

5习题2.2第5题答案

(1)a2-b2

(2)a2-2ab+b2

(3)a2-b2

6习题2.2第6题答案

原式=am-bm-(-bn+an)=(a-b)m-(a-b)n

7习题2.2第7题答案

(1)原式=3a+2b+8c+2a-3b-5c

=(3a+2a)+(2b-3b)+(8c-5c)

= 5a–b+3c

(2)原式=2xy+x2-y2-x2+y2+3xy

=(x2-x2)+(-y2+y2)+(2xy+3xy)

= 5xy

(3)原式=3x2-(5x+4x-5-9x2

=3x2-5x-4x+5+9x2

=(3x2+9x2)+(-5x-4x)+5 

= 12x2-9x+5

沪科版七年级上册数学书答案

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