76,010 views
28 votes
28 votes
f(x) = x3 – 7x + 6 (a) Show that (x – 2) is a factor of f (x). (b) Hence, or otherwise, factorise f(x) completely.

User Ayman Mahgoub
by
3.3k points

1 Answer

14 votes
14 votes

Answer:

see explanation

Explanation:

if (x - h) is a factor of f(x) then f(h) = 0

(a)

if (x - 2) is a factor of f(x) then f(2) = 0

f(2) = 2³ - 7(2) + 6

= 8 - 14 + 6

= - 6 + 6

= 0

since f(2) = 0 then (x - 2) is a factor of f(x)

(b)

using synthetic division to factor f(x)

insert a zero in the x² position on the table

2 | 1 0 - 7 6

↓ 2 4 - 6

-----------------------

1 2 - 3 0

quotient is

x² + 2x - 3 = (x + 3)(x - 1)

Then

f(x) = (x - 2)(x + 3)(x - 1)

User Nilaksha Perera
by
3.0k points