1)2√18=2*3√2=6√2
2)2√75=2*5√3=10√3
3)6√3*3√3=18*3=54
4)3√2*2√2=6*2=12
<span> (3x +y)^2 - (3x - y)^ + (3xy
- 1 )^2 =<span>
=(
3x+y+3x-y)(3x+y - 3x+y)+ (3xy - 1 )^2 =
= 6x*2y+
9x^y^2 - 6 xy +1= 12xy + 9 x^2y^2 - 6 xy + 1 =
<span>= 9x^2
y^2 + 6 xy +1 =(3xy + 1)^2</span></span></span>