第63页 - 江苏版实验班提优训练数学七年级上下册答案

B

xy(x-2)(x+2)

(a+b)(a+b+2)(a+b-2)

m(x-2)(m-1)(m+1)

a(b-2)²

$ \begin{aligned}解：原式&=5b(a²-4ab+4b²) \\ &=5b(a-2b)². \\ \end{aligned}$

$ \begin{aligned}解：原式&=(x²+1-x²+9)(x²+1+x²-9) \\ &=10(2x²-8) \\ &=20(x²-4) \\ &=20(x-2)(x+2). \\ \end{aligned}$

$ \begin{aligned}解：原式&=(x+y)(x-y)+a(x+y) \\ &=(x+y)(x-y+a). \\ \end{aligned}$

$ \begin{aligned}解：原式&=(x²-2x)²+2(x²-2x)-8+9 \\ &=(x²-2x)²+2(x²-2x)+1 \\ &=(x²-2x+1)² \\ &=(x-1)⁴. \\ \end{aligned}$

B

D

(a-b)(x+2y)(x-2y)

$-a(a-1)² $

$ 原式=mn(m+n).$

$ ∵m+n=4，mn=-1，$

$∴原式=-1×4=-4.$

$ \begin{aligned}解：原式&=m²n²+2m²+2n²+4 \\ &=(mn)²+2(m²+n²)+4 \\ &=(mn)²+2(m+n)²-4mn+4. \\ \end{aligned}$

$ ∵m+n=4，mn=-1，$

$ \begin{aligned} ∴原式&=(-1)²+2×4²-4×(-1)+4 \\ &=1+32+4+4 \\ &=41. \\ \end{aligned}$