Let f(x) = x4 – 7x3 + 9x2 + 7x- 10
Constant term = -10
Factors of -10 are ±1, ±2, ±5, ±10
Let x – 1 = 0 or x = 1
f(1) = (1)4 – 7(1)3 + 9(1)2 + 7(1) – 10
= 1 – 7 + 9 + 7 - 10
= 0
f(1) = 0
Let x + 1 = 0 or x = -1
f(-1) = (-1)4 – 7(-1)3 + 9(-1)2 + 7(-1) – 10
= 1 + 7 + 9 – 7 - 10
= 0
f(-1) = 0
Let x – 2 = 0 or x = 2
f(2) = (2)4 – 7(2)3 + 9(2)2 + 7(2) – 10
= 16 – 56 + 36 + 14 – 10
= 0
f(2) = 0
Let x – 5 = 0 or x = 5
f(5) = (5)4 – 7(5)3 + 9(5)2 + 7(5) – 10
= 625 – 875 + 225 + 35 – 10
= 0
f(5) = 0
Therefore, (x – 1), (x + 1), (x – 2) and (x - 5) are factors of f(x)
Hence f(x) = (x – 1) (x – 1) (x – 2) (x - 5).
