1. g ( x ) = 5 x − 4 3 D : 5 x − 4 = 0 → 5 x = 4 / : 5 → x = 5 4 → x ∈ R \ { 5 4 } 2. h ( x ) = x − 5 x D : x ≥ 0 ∧ x − 5 = 0 → x ≥ 0 ∧ x = 5 → x ∈ ⟨ 0 ; ∞ ) \ { 5 }
3. f ( x ) = x 2 − 5 x x D : x ≥ 0 ∧ x 2 − 5 x = 0 → x ≥ 0 ∧ x ( x − 5 ) = 0 → x ≥ 0 ∧ x = 0 ∧ x = 5 → x ∈ R + \ { 5 } 4. g ( x ) = x 2 − x − 20 x + 5 D : x ≥ 0 ∧ x 2 − x − 20 = 0 → x ≥ 0 ∧ ( x + 4 ) ( x − 5 ) = 0 → x ≥ 0 ∧ x = − 4 ∧ x = 5 → x ∈ ⟨ 0 ; ∞ ) \ { − 4 ; 5 }
5. h ( x ) = x 2 + 1 3 D : x 2 + 1 = 0 → x 2 = − 1 → x ∈ R 6. f ( x ) = x + 1 x − 2 D : x − 2 ≥ 0 ∧ x + 1 = 0 → x ≥ 2 ∧ x = − 1 → x ∈ ⟨ 2 ; ∞ )
7. g ( x ) = 3 x 2 − x − 2 x 2 D : 3 x 2 − x − 2 = 0 → ( 3 x + 2 ) ( x − 1 ) = 0 → x = − 3 2 ∧ x = 1 → x ∈ R \ { − 3 2 ; 1 } 8. h ( x ) = 3 ( x − 4 ) 2 − 7 D : x ∈ R
The domains for the functions are identified by avoiding undefined situations like division by zero or negative square roots. Each function has been analyzed step-by-step to determine its respective domain in interval notation. Domains vary from all real numbers to specific intervals excluding certain values.
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