1.在7xy-5kx³y的四次方与1/2x²y的四次方-6x³y的四次方的差不含x³y的四次方项,求k的值.
(7xy-5kx³y^4)-(1/2x²y^4-6x³y^4)
=7xy-5kx³y^4-1/2x²y^4+6x³y^4
=7xy+(-5k+6)x³y^4-1/2x²y^4
∵ 差不含x³y^4的项
∴-5k+6=0
-5k=-6
k=6/5
2.已知c
1.在7xy-5kx³y的四次方与1/2x²y的四次方-6x³y的四次方的差不含x³y的四次方项,求k的值.
(7xy-5kx³y^4)-(1/2x²y^4-6x³y^4)
=7xy-5kx³y^4-1/2x²y^4+6x³y^4
=7xy+(-5k+6)x³y^4-1/2x²y^4
∵ 差不含x³y^4的项
∴-5k+6=0
-5k=-6
k=6/5
2.已知c