f(x)=x4-16 find f(1-√2)
The best way is by the remainder theorem using synthetic division:
Write x4-16 as x4+0x3+0x2+x-16
1-√2|1 0 0 0 -16
|
1
1-√2|1 0 0 0 -16
| 1-√2
1 1-√2
Multiply (1-√2)(1-√2) = 1-2√2+2 = 3-2√2
1-√2|1 0 0 0 -16
| 1-√2 3-2√2
1 1-√2 3-2√2
Multiply (3-2√2)(1-√2) = 3-5√2+2·2 = 3-5√2+4 = 7-5√2
1-√2|1 0 0 0 -16
| 1-√2 3-2√2 7-5√2
1 1-√2 3-2√2 7-5√2
Multiply (7-5√2)(1-√2) = 7-12√2+5·2 = 7-12√2+10 = 17-12√2
1-√2|1 0 0 0 -16
| 1-√2 3-2√2 7-5√2 17-12√2
1 1-√2 3-2√2 7-5√2 1-12√2
Answer: 1-12√2
Edwin