Đáp án:
Giải thích các bước giải:
`d, 8 x ^2 − 2 x − 1`
`= 8 x ^2− 4 x + 2 x - 1`
`= 4 x ( 2 x - 1 ) + ( 2 x - 1 )`
`= ( 2 x − 1 ) ( 4 x + 1 )`
`e, x ^5 + x − 1`
`= x ^5 + x ^2 − x^ 2 + x - 1 `
`= x ^2 ( x ^3 + 1 ) − ( x^ 2 − x + 1 )`
`= x ^2 ( x + 1 ) ( x^ 2 − x + 1 ) − ( x^ 2 − x + 1 )`
`= (x ^3 + x^2 ) ( x^ 2 − x + 1 ) − ( x^ 2 − x + 1 )`
`= ( x^ 2 − x + 1 ) ( x^ 3 + x ^2 − 1 )`
`f, 4 x ^4 + 81`
`= 4 x ^4 + 36 x^ 2 + 81 − 36 x ^2`
`= (2x ^2)^2 + 2. 2 x^ 2 . 9 + 9^2 − 36 x ^2`
`= ( 2 x^ 2 + 9 )^ 2 − (6 x )^ 2`
`= ( 2 x^ 2 + 9− 6 x ) ( 2 x ^2 + 9+ 6 x )`