4.5 x 10 to the power of 4
        
             
        
        
        
Answer:
A
Step-by-step explanation:
 
        
                    
             
        
        
        
A number is rational if it can be written in form a/b where a and b are integers and b is not equal to 0
integers are like -4,-3,-2,-1,0,1,2,3,4, etc
so
√20=2√5 which is irrational because we can't write it as a fraciton with only integers
also a rational number multilied by an irratinonal number=irrtaional
we know that the square root of any prime number will be irrational and 5 is prime so 2 times √5=rational times irrational=irrational
√20 is irrational