adding and subtracting radical expression

−3√ ​180 ​ ​​ + 4√ ​45 ​ ​​ =

-3 √ [ 4 * 45 ]  + 4 √45  =

-3 √4*√45 + 4√45  =

-3 *2 *√45 + 4√45 =

-6√45 + 4√45  =

-2√45  =

-2* √9 * √5  =

-2 * 3 * √5  =

-6√5