Question

if 3 is the zero of the polynomial x square +2x-a? find a?

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Answer 1

$x {}^{2} + 2x - a$

3 is 0 of the polynomial so, x = 3

${3}^{2} + 2 \times 3 - a = 0 \\ 9 + 6 - a = 0 \\ 15 - a = 0 \\ 15 = a \\ a = 15$

Hope it helps

Answer 2

Answer:

• The value of a is 15.

Given:

=> 3 is the zero of the polynomial is x² + 2x - a

To find:

• The value of a.

Solution:

⠀⠀⠀=> f (x) = x² + 2x - a; f (x) = 0

Substitute x = 3, in the given quadratic polynomial

⠀⠀⠀>> f (3) = 3² +2(3) - a

⠀⠀⠀>> 9 + 6 - a = 0

⠀⠀⠀>> a = 15

Therefore, the value of a is 15.

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Verification:

⠀⠀⠀=> x² + 2x - a = 0

Substituting a = 15, we get

⠀⠀⠀=> x² + 2x - 15 = 0

⠀⠀⠀>> x² + 5x - 3x - 15 = 0

⠀⠀⠀>> x (x + 5) - 3 (x + 5) = 0

⠀⠀⠀>> (x + 5) (x - 3) = 0

⠀⠀⠀>> x = -5 or 3

Hence, verified.

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Extra information:

• If one of the zero of quadratic polynomial is 1, then the other zero of the polynomial is c/a.

• If one of the zero of the quadratic polynomial is -1, then the other zero of the polynomial is -c/a.