负根号256=-√256
=-√(16²)
=-16
正负根号361=±√361
=±√(19²)
=±19
根号25+根号16减根号9
=√25+√16-√9
=√(5²)+√(4²)-√(3²)
=5+4-3
=6
根号25²-24²
=√(25²-24²)
=√[(25+24)(25-24)]
=√(49×1)
=√49
=√(7²)
=7
16x²=25
(4x)²=(±5)²
4x=5或4x=-5
x=5/4或x=-5/4
225(x-1)²=49
[15(x-1)]²=(±7)²
15(x-1)=±7
15(x-1)=7或15(x-1)=-7
15x-15=7或15x-15=-7
x=22/15或x=8/15