八年级数学帮助

（1）6x^2*3xy
=6*3x^3y
=18x^3y

(2)2ab^2*(-3ab)
=2*(-3)a^2b^3
=-6a^2b^3

(3)4x^2y*(-xy^2)^3
=4x^2y*(-x^3y^6)
=4*(-1)x^5y^7
=-4x^5y^7

(4)(1.3*10^5)(3.8*10^3)
=1.3*3.8*10^8
=4.94*10^8

(5)a^n*x^2*(a^n+x^2y)
=a^n*x^2*a^n+a^n*x^2*x^2y
=a^2n*x^2+a^nx^4y

(6)ab前面的系数是2还是3 呀？
(-16a^2bc)*(1/3ab)
=-16/3a^3b^2c
或者
(-16a^2bc)*(1/2ab)
=-16/2a^3b^2c
=-8a^3b^2c

18乘x的3次方再乘y