第83页 - 经纶学典学霸七年级数学上下册【江苏国标】

-16n

2或12

42°

19

-1

$\frac{5}{2}或\frac{11}{3}或\frac{31}{3} $

$ \begin{aligned}解：原式&=-4+\frac{3}{2}+1 \\ &=-\frac{3}{2} \\ \end{aligned}$

$ \begin{aligned}解：原式&=a⁶+4a⁶+a⁶ \\ &=6a⁶. \\ \end{aligned}$

$ \begin{aligned}解：原式&=x²-9-x²+4x-4 \\ &=4x-13 \\ \end{aligned}$

$ \begin{aligned}解：原式&=[m+(2n-3)][m-(2n-3)] \\ &=m²-(2n-3)² \\ &=m²-4n²+12n-9 \\ \end{aligned}$

$ \begin{aligned}解：原式&=a²(x-y)-16(x-y) \\ &=(x-y)(a²-16) \\ &=(x-y)(a+4)(a-4) \\ \end{aligned}$

$ \begin{aligned}解：原式&=(5a+5b)²-(3a-3b)² \\ &=(5a+5b+3a-3b)[5a+5b-(3a-3b)] \\ &=(8a+2b)(2a+8b) \\ &=4(4a+b)(a+4b) \\ \end{aligned}$

$ \begin{aligned}解：原式&=(x+y)(x²+2xy+y²) \\ &=(x+y)(x+y)² \\ &=(x+y)³ \\ \end{aligned}$

7