Verified answer

If you mean: x ≤ −3 or x = 3, then:

(−∞,−3] U {3}

or

(−∞,−3] U [3,3]

Yes

( -infinity, 3] U [3]

x </= 3 ......... ( - 00 , 3 ]

x = 3 ......... [ 3 , 3 ] this is not used much

x ≤ -3, x = 3

(-∞,-3) U [3,3]