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Let a polynomial be defined by:
f(x) = x(x + 6)(x - 2) and
f(x) = x³ + 4x² - 12x
a. Name all zeros of the function.

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Explanation:

a polynomial of degree n (that means the highest exponent of x is n) must have n zeroes.

in our case that means 3 zeroes.

the best way to find them is to have the factorial form of the polynomial : to see how several terms are multiplied to give us the polynomial.

the first f(x) gives us exactly that (the second f(x) is just the form with all the multiplications done) :

f(x) = x(x + 6)(x - 2)

when is the product of factors 0 ?

only when at least one factor is 0.

so, let's see,

when is x 0 ? well, x = 0.

when is (x + 6) = 0 ? x = -6.

when is (x - 2) = 0 ? x = 2.

so, the 3 zeroes are

x = -6

x = 0

x = 2

User Stefano Giacone
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