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1 vote
For the following function, one zero is given. Find all other zeros.

f(x)=x3-7x2+17x-15; 2-i

User Max Strini
by
4.6k points

1 Answer

5 votes

Answer:

1,-3,-5

Explanation:

Given:

f(x)=x^3+7x^2+7x-15

Finding all the possible rational zeros of f(x)

p= ±1,±3,±5,±15 (factors of coefficient of last term)

q=±1(factors of coefficient of leading term)

p/q=±1,±3,±5,±15

Now finding the rational zeros using rational root theorem

f(p/q)

f(1)=1+7+7-15

=0

f(-1)= -1 +7-7-15

= -16

f(3)=27+7(9)+21-15

=96

f(-3)= (-3)^3+7(-3)^2+7(-3)-15

= 0

f(5)=5^3+7(5)^2+7(5)-15

=320

f(-5)=(-5)^3+7(-5)^2+7(-5)-15

=0

f(15)=(15)^3+7(15)^2+7(15)-15

=5040

f(-15)=(-15)^3+7(-15)^2+7(-15)-15

=-1920

Hence the rational roots are 1,-3,-5 !

User Jim Wolff
by
6.1k points
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