2/9 + 4√5 = a + b√5
As per the rule in maths, the first term of left hand side will be equal to first term of right hand side (in this type of question)
So, 2/9 = a and 4√5 = b√5
2/9 = a and (√5 is common in both i.e 4√5 and b√5)
So, it will get cancelled
a = 2/9 and b = 4