(1)81x²-18x+1
=(9x-1)²
(2)0.36a²+1-1.2a
=(0.6a-1)²
(3)(x+y)²+10(x+y)+25
=(x+y+5)²
(4)-2x³y-2xy³+4x²y²
=-2xy(x²-2xy+y²)
=-2xy(x-y)²
(1)81x²-18x+1
=(9x-1)²
(2)0.36a²+1-1.2a
=(0.6a-1)²
(3)(x+y)²+10(x+y)+25
=(x+y+5)²
(4)-2x³y-2xy³+4x²y²
=-2xy(x²-2xy+y²)
=-2xy(x-y)²