Question

factorise 6x³ - 3x² - 9x - 5
​

Answer 1

Answer:

x3 3x2 - 9x - 5

Let p(x)=X° - 3x^2- 9x - 5

By trial, we find that p- 1) = (-1)3 -3(-1)2- 9(-1)-5 1-3+9- 5 = 0

By Factor Theorem, x - (- 1), i.e., (x + 1) is a factor of p(x).

Now, x3- 3x2- 9x - 5 = x2(x + 1) - 4x(x + 1) - 5(x + 1) = (x + 1)(x2- 4x - 5) = (X+ 1)(x - 5x + X - 5) = (x+ 1){x(x - 5) + 1 (x - 5)} (X+ 1) X - 5)(X + 1).