a)√(810·40)=√(9²·2²·10²)=3·2·10=60
b)√(90·6,4)=√(3²·10·64/10)=√(3²·8²)=3·8=24
c)√(16,9·9·0,4)=√(169/10·3²·4/10)=√(13²·3²·2²)/10²=(13·3·2)/10=78/10=7,8
d)√63·√7=√(7·3²·7)=7·3=21
e)√1,2·√3intreg1/3=√12/10·√10/3=√(12·10/10·3)=√12/3=√4=2
f)√36/25+√81/25=6/5+9/5=15/5=3
g)3√20-3√45+4√5=3√(2²·5)-3√(3²·5)+4√5=3·2√5-3·3√5+4√5=6√5-9√5+4√5=-3√5+4√5=√5
h) (2-√3)²=4-2·2·√3+3=4+3-4√3=7-4√3
i)(√5-2)((√5+2)=5-4=1
j)(6-√2)²-(5+√2)²=36-2·6√2+2-(25+2·5√2+2)=38-12√2-27+10√2=12-2√2=2(6-√2)