第62页 - 经纶学典学霸七年级数学上下册【江苏国标】

C

D

10

218

±3

±2

-6或0

$ \begin{aligned}解：原式&=4m²+12mn+9n²-(4m²-n²) \\ &=4m²+12mn+9n²-4m²+n² \\ &=10n²+12mn. \\ \end{aligned}$

$ \begin{aligned}解：原式&=[(m+2n)(m-2n)]² \\ &=(m²-4n²)² \\ &=m⁴-8m²n²+16n⁴ \\ \end{aligned}$

$ \begin{aligned}解：原式&=[x-(3y+2)]² \\ &=x²-2x(3y+2)+(3y+2)² \\ &=x²+9y²-6xy \\ &=4x+12y+4. \\ \end{aligned}$

$ \begin{aligned}解：原式&=[a-(2b-3c)][a+(2b-3c)] \\ &=a²-(2b-3c)² \\ &=a²-(4b²-12bc+9c²) \\ &=a²-4b²+12bc-9c² \\ \end{aligned}$

$ \begin{aligned}解：原式&=x²-16+x²-6x+9 \\ &=2x²-6x-7 \\ \end{aligned}$

$因为x=3$

$所以原式=2×3²-6×3-7=-7$

$ \begin{aligned}解：原式&=x²-4y²-4x²+4xy-y²+6x²-15xy-2xy+5y² \\ &=3x²-13xy \\ \end{aligned}$

$将x=-1，y=-2代入$

$得3x²-13xy=3×(-1)²-13×(-1)×(-2)=-23$

C

D