text: help any one. . . .how do you add radical expressions (mathmatically)? does anyone know step by step how to add(+) radical expressions. i am studying it in my high school math class and i have not yet learned to add these expressions yet some help from my fellow yahooers would be really nice. thanx. the radicals must be "the same" before you can add or subtract them! for example you can add 3√2 + 5√2. you treat the radical part like a variable  3√2 + 5√2= (3+5)√2  =8√2 to make sure you can add radicals first you must simplify them. lets do your example: 3√20 + √45 + 2√5 step one : simplifying √20 and √45, since √5 is in its simplest form we just leave it like that.  3√20 + √45 + 2√5=  =3√(5x4)+√(9x5)+2√5= =3√(5x2^2)+√(3^2x5)+2√5  since √a^2=a     and √(axb)=√a x √b (x means times) we get  3√5√2^2+√3^2√5+2√5= 3x2√5+3√5+2√5= 6√5+3√5+2√5= (6+3+2)√5= 11√5