Question

Factorise
x³ - 3x² - 9x -5​

Answer 1

By a direct checking

f(5) = 0 where f(x) = x^3 - 3x^2 - 9x - 5.

Thus, f(x) = x^2(x- 5) + 2x(x - 5) + (x - 5)

= (x-5)( x^2 + 2x + 1)

= (x-5)(x + 1)^2.

One can also check that f(-1) = 0 & proceed accordingly.

hope this helps you....plz Mark as Brainliest answer

Answer 2

Step-by-step explanation:

Given :

A polynomial x^3 - 3x^2 - 9x - 5

To Find :

Three factors of polynomial x^3 - 3x^2 - 9x - 5

Solution :

Constant Term = -5

Factors of Constant Term = 1,5

Putting x = 1 :

→ (1)^3 - 3(1)^2 - 9(1) - 5

→ 1 - 3 - 9 - 5

→ 1 - 17

→ - 16

Putting x = -1 :

→ (-1)^3 - 3(-1)^2 -9(-1) - 5

→ - 1 - 3 + 9 - 5

→- 4 + 9 - 5

→5 - 5

→ 0

x = -1 is the root .

x + 1 is the factor.

(Refer to the attachment)

Now :

→ x^2 - 4x - 5

→ x^2 - (5x - 1x) - 5

→ x^2 - 5x + 1x - 5

→x(x - 5) + 1(x - 5)

→ (x + 1)(x - 5)

So , The three factors are (x+1) , (x-5) , (x+1)...