Q1 of 47 Page 80

Determine whether (x + 1) is a factor of the following polynomials:

3x3 + 8x2 + 6x – 5

Let f(x) = 3x3 + 8x2 + 6x – 5


By factor theorem,


x + 1 = 0 ;x = – 1


If f(– 1) = 0 then (x + 1) is a factor of f(x)


∴f(– 1) = 3(– 1)3 + 8(– 1)2 – 6(– 1) – 5


= – 3 + 8 + 6 – 5 = 6(not equal to 0)


∴(x + 1) is not a factor of f(x) = 3x3 + 8x2 + 6x – 5


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