X4 + +X3 2X− =4 0 HD

Bài 16: Giải phương trình: x

⁴

+ +x

³

2x− =4 0 HD: ^=x

⁴

^+x

³

^{+2x− = =4 0}

(

^x−1

)(

^x+2

) (

^x

²

⁺²

)

⁼⁰HD: ^x

⁴

^−30x

²

^{+31x−30 0= =x}

⁴

^{+ −x 30}

(

^x

²

^{− + =x 1}

)

⁰

(

³

^{1 30}

) (

²

¹

)

⁰

(

¹

) (

²

^{1 30}

) (

²

¹

)

⁰x x x x x x x x x x= + − − + = = + − + − − + =

(

^x

²

^{x 1}

)(

^x

²

^{x 30}

)

⁰= − + + − = , Vì ^x

²

^{− + =x 1 }_^x−1₂^_

²

^{+  =3}₄ ^{0 x}

²

^{+ −x 30 0= =}

(

^x+6

)(

^x−5

)

⁼⁰ 