SSC CGL Tier II 12 Jan 2017 Paper 1

Question : 75 of 100

Marks: +1, -0

If x, y, z are the three factors of

a^ 3 – 7a – 6

, then value of (x + y + z) will be

Solution:

(1)

a^{3}-7 a-6=0

When

a=-1

f(a)=-1+7-6=0

∴(a+1)

is a factor.

{a^3-7a-6}/{a+1}=a^2-a-6

∴ a^{2}-a-6=a^{2}-3 a+2 a-6

=a(a-3)+2(a-3)

=(a-3)(a+2)

∴ x+y+z

=a+1+a-3+a+2=3 a

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