Question

七年级下册数学课本北师版习题答案

我要第一章总复习的下册，谢啦，各位！

Answer 1

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：

Answer 2

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