Question

Factorize using factor theorem
x^3-2x-7x+2​

Answer 1

Answer:

Let f(x) = x3 + 2x2 – x – 2

Constant term = -2

Factors of -2 are ±1, ±2

Let x – 1 = 0

⇒ x = 1

Put the value of x in f(x)

f(1) = (1)3 + 2(1)2 – 1 – 2

= 1 + 2 – 1 – 2

= 0

So, (x – 1) is factor of f(x)

Let x + 1 = 0

⇒ x = -1

Put the value of x in f(x)

f(-1) = (-1)3 + 2(-1)2 – 1 – 2

= -1 + 2 + 1 – 2

= 0

(x + 1) is a factor of f(x)

Let x + 2 = 0

⇒ x = -2

Put the value of x in f(x)

f(-2) = (-2)3 + 2(-2)2 – (-2) – 2

= -8 + 8 + 2 – 2

= 0

(x + 2) is a factor of f(x)

Let x – 2 = 0

⇒ x = 2

Put the value of x in f(x)

f(2) = (2)3 + 2(2)2 – 2 – 2

= 8 + 8 – 2 – 2

= 12 ≠ 0

(x – 2) is not a factor of f(x)

Hence f(x) = (x + 1)(x - 1)(x + 2)