x 2 − 25 x 2 + 6 x + 5 = ( ∗ ) ; x 2 − 25 = 0 → x 2 = 25 → x = − 5 ∧ x = 5 x 2 + 6 x + 5 = 0 Δ = 6 2 − 4 ⋅ 1 ⋅ 5 = 36 − 20 = 16 ; Δ = 16 = 4 x 1 = 2 ⋅ 1 − 6 − 4 = 2 − 10 = − 5 ; x 2 = 2 ⋅ 1 − 6 + 4 = 2 − 2 = − 1 x 2 + 6 x + 5 = ( x + 5 ) ( x + 1 )
( ∗ ) = ( x − 5 ) ( x + 5 ) ( x + 5 ) ( x + 1 ) = x − 5 x + 1
x 2 − 25 x 2 + 6 x + 5 = ( x − 5 ) ( x + 5 ) x 2 + 6 x + 5 = ( ∗ ) . x − 5 = 0 an d x + 5 = 0 ⇒ x ∈ R ∖ { 5 ; − 5 } x 2 + 6 x + 5 = ( x + 5 ) ( x + 1 ) b ec a u se : Δ = 6 2 − 4 ⋅ 1 ⋅ 5 = 36 − 20 = 16 ⇒ Δ = 16 = 4 x 1 = 2 ⋅ 1 − 6 − 4 = 2 − 10 = − 5 , x 2 = 2 ⋅ 1 − 6 + 4 = 2 − 2 = − 1 ( ∗ ) = ( x − 5 ) ( x + 5 ) ( x + 5 ) ( x + 1 ) = x − 5 x + 1
To simplify x 2 − 25 x 2 + 6 x + 5 , we can factor both the numerator and the denominator, resulting in ( x − 5 ) ( x + 5 ) ( x + 1 ) ( x + 5 ) . After canceling the common factor ( x + 5 ) , the simplified expression is x − 5 x + 1 , with the restriction that x = − 5 and x = 5 .
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