計算:(-1/2x^2y)^3·(-3xy^2)^2

計算:(-1/2x^2y)^3·(-3xy^2)^2


(-1/2x^2y)^3·(-3xy^2)^2
=(-1/8x^6y^3)·(9x²;y^4)
=-9/8x^8y^7



計算:(x^2y)^2*(-3xy^3)*(-6x^2y^4)


:(x^2y)^2*(-3xy^3)*(-6x^2y^4)
=x^4y²;×18x³;y^7
=18x^7y^9



計算:3xy(2x^2y-1/3xy^2)


6yx^(2y+1)-1/y



已知x+y=3,x2+y2-3xy=4.求下列各式的值:(1)xy; ; ;(2)x3y+xy3.


(1)∵x+y=3,∴(x+y)2=9,∴x2+y2+2xy=9,∴x2+y2=9-2xy,代入x2+y2-3xy=4,∴9-2xy-3xy=4,解得:xy=1.(2)∵x2+y2-3xy=4,xy=1,∴x2+y2=7,又∵x3y+xy3=xy(x2+y2),∴x3y+xy3=1×7=7.