2xy^2+4x^2y
=xy(2y+4x)
=2xy(y+2x)
=(2*1/4)*5
=5/2
(1)
A^2B-B^3
=B(A^2-B^2)
=B(A-B)(A+B)
(2)
-4A^2B^2+8A^2B-2AB
=AB(-4AB+8A-2)
=-2AB(2AB-4A+1)
解方程组：
x-3y=1
2x+y-15=1
整理得:
x=1+3y (1)
2x+y=16 (2)
(1)代入(2)得:
2(1+3y)+y=16
2+6y+y=16
2+7y=16
7y=14
y=2
解方程组得:
x=7
y=2