七年级下册数学课本北师版习题答案
答案:2 悬赏:40 手机版
解决时间 2021-02-16 04:04
- 提问者网友:太高姿态
- 2021-02-15 16:15
我要第一章总复习的下册,谢啦,各位!
最佳答案
- 五星知识达人网友:大漠
- 2021-02-15 16:47
解:(1) (3k²+7k)+(4k²-3k+1)
=3k²+7k+4k²-3k+1
=3k²+4k²+7k-3k+1
=7k²+4k+1
(2) (3x²+2xy-1/2x)-(2x²-xy+x)
=3x²+2xy-1/2x-2x²+xy-x
=3x²-2x²+2xy+xy-1/2x-x
=x²-3/2x+3xy
=x(x-3/2+3y)
(3) (7a²+2a+b)-(3a²+2a-b)
=4a²+2a+b-3a²-2a+b
=4a²+2b
=2(2a²+b)
(4) (1/2xy+y²+1)+(x²-1/2xy-2y²-1)
=1/2xy+y²+1+x²-1/2xy-2y²-1
=x²+y²-2y²+1/2xy-1/2xy+1-1
=x²-y²
=(x+y)(x-y)
2.求下列整式的值:
=3k²+7k+4k²-3k+1
=3k²+4k²+7k-3k+1
=7k²+4k+1
(2) (3x²+2xy-1/2x)-(2x²-xy+x)
=3x²+2xy-1/2x-2x²+xy-x
=3x²-2x²+2xy+xy-1/2x-x
=x²-3/2x+3xy
=x(x-3/2+3y)
(3) (7a²+2a+b)-(3a²+2a-b)
=4a²+2a+b-3a²-2a+b
=4a²+2b
=2(2a²+b)
(4) (1/2xy+y²+1)+(x²-1/2xy-2y²-1)
=1/2xy+y²+1+x²-1/2xy-2y²-1
=x²+y²-2y²+1/2xy-1/2xy+1-1
=x²-y²
=(x+y)(x-y)
2.求下列整式的值:
全部回答
- 1楼网友:不甚了了
- 2021-02-15 17:53
不知道啊
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