Question

1/sqrt18-sqrt32=

Answer 1

sqrt(18) = 3*sqrt(2)
sqrt(32) = 4*sqrt(2)

Answer 2

We do not like radical in the denominator, so we rationalize by multiplying by sqrt(2) / sqrt(2):
1/sqrt(18) = 1/[3*sqrt(2)] = sqrt(2) / 6

Answer 3

1/sqrt(18) - sqrt(32) = (1/6)*sqrt(2) - 4*sqrt(2)
= -(23/6)*sqrt(2)