5/(sqrt)5 = 5 times (sqrt)5/5, when you rationalize the denominator by multiplying by (sqrt)5/(sqrt)5, which is the same as one, and you can simplify that down to just (sqrt)5.
0.625
25
16
2.5
There is no square root of -75. If it's 75, that is 5 square root 3.
2 square root of 5
0.4
0.625
25
12
Square root (75) / square root (3) = 5
12
0.4545
25
5
25
It is 5/6*sqrt(3).