Question

Write the following in roster form

{x ∈ N : 4x + 9 < 52}

Answer 1

4x + 9 < 52

4x + 9 – 9 < 52 – 9

4x < 43

x < `43/4`

x < 10.75 

But x ∈ N

The problem specifies that x must be a natural number:

∴ N = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10}

The natural numbers that are strictly less than 10.75 are all integers from 1 up to 10.