第14页 - 江苏版实验班提优训练数学七年级上下册答案

$\frac{5}{2}或-\frac{3}{2} $

6

3

4

$7或\frac{931}{25} $

$ \begin{aligned}解：原式&=(-y)²-x²+x²+2xy+y² \\ &=2y²+2xy. \\ \end{aligned}$

$ \begin{aligned}解：原式&=(x²-4y²)(x²-4y²) \\ &=(x²-4y²)² \\ &=x⁴-8x²y²+16y⁴. \\ \end{aligned}$

$ \begin{aligned} 解：原式&=[(a+3b)(a-3b)]² \\ &=(a²-9b²)² \\ &=a⁴-18a²b²+81b⁴. \\ \end{aligned}$

$ \begin{aligned}解：原式&=a²+2ab+b²+a²-9b² \\ &=2a²+2ab-8b². \\ \end{aligned}$

$ \begin{aligned} 解：原式&=(4x²)²-2·4x²·y²+(y²)² \\ &=(4x²-y²)² \\ &=(2x+y)²(2x-y)². \\ \end{aligned}$

$ \begin{aligned}解：原式&=(x-y)(a²-9b²) \\ &=(x-y)(a+3b)(a-3b). \\ \end{aligned}$