What are the zeros of the parabola whose equation is y = x2 + 8x + 15 (1)
-5 and -3
(3)
-5 and 3
(2)
5 and 3
(4)
5 and -3

9514 1404 393

  (1)  -5 and -3

Step-by-step explanation:

Descarte's rule of signs tells you the lack of sign changes among the coefficients means there are no positive real roots. That eliminates all answer choices except the first one.

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If you want to go to the trouble, you can factor the equation:

  y = (x +3)(x +5)

These factors are zero when x = -5 and x = -3.

step-by-step explanation:

first, eliminate the parenthesis:

3

x

+

2

−

4

x

second, group like terms:

3

x

−

4

x

+

2

third, combine like terms:

(

3

−

4

)

x

+

2

→

−

1

x

+

2

→

−

x

+

2

x² + 3x + 7 = 0       [ax² + bx + c]

a = 1

b = 3

c = 7

quadratic formula:

    (+/- is this ±)

plug in the numbers into the variables

your answer is a