d) $\frac{-30}{5}$ < x < $\frac{-45}{9}$
=> -6 < x < -5
=> x ∈ ∅
=> A = { x / x ∈ ∅}
Vậy A = { x/ x ∈ ∅ }
a) $\frac{-28}{4}$ < x < $\frac{-21}{7}$
=> -7 < x < -3
=> x ∈ { -7 ; -6 ; -5 ; -4 }
=> A = { -7 ; -6 ; -5 ; -4 }
Vậy A = { -7 ; -6 ; -5 ; -4 }
b) $\frac{-30}{6}$ < x < $\frac{-28}{14}$
=> -5 < x < -2
=> x ∈ { -4 ; -3 }
=> A = { -4 ; -3 }