3 square root of 5+square root of 20-square root of 45
√5 + √20 - √45
√5 = √(1*5) = √(5)
√20 = √(4*5) = 2√5
√45 = √(9*5) = 3√5
Now we can substitute these values back into the original expression:
√5 + 2√5 - 3√5
= (1 + 2 - 3)√5
= 0√5
= 0
Therefore, the simplified expression is 0.