第62页

信息发布者：
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
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