当k为何值时,多项式2(2x²-3xy-2y²)-(2x²+2kxy+b²)中不含xy项
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当k为何值时,多项式2(2x²-3xy-2y²)-(2x²+2kxy+b²)中不含xy项
当k为何值时,多项式2(2x²-3xy-2y²)-(2x²+2kxy+b²)中不含xy项
当k为何值时,多项式2(2x²-3xy-2y²)-(2x²+2kxy+b²)中不含xy项
2(2x²-3xy-2y²)-(2x²+2kxy+b²)
=4x²-6xy-4y²-2x²-2kxy-b²
=2x²-(6+2k)xy-4y²-b²
6+2k=0
k=-3
-6-2k=0
k=-3
2(2x²-3xy-2y²)-(2x²+2kxy+b²)=2x²-(6+2k)xy-4y²-b² 当k=-3时,不含xy项
-3
要想多项式不含x,y 只需x=y 将多项式化简得 -8x²-2kx²-b² 令k=-4 就行了