Which of the following uses the substitution method to solve linear-quadratic system y=x2−4x−41

, y=4
?(1 point)
Responses

(−5,4)
left parenthesis negative 5 comma 4 right parenthesis

(9,4)
left parenthesis 9 comma 4 right parenthesis

(−5,4)
and (9,4)
left parenthesis negative 5 comma 4 right parenthesis and left parenthesis 9 comma 4 right parenthesis

(5,4)
and (−9,4)

1 answer

To solve the linear-quadratic system using the substitution method, we can follow these steps:

  1. We have the equations: \[ y = x^2 - 4x - 41 \] \[ y = 4 \]

  2. Substitute \( y = 4 \) into the quadratic equation: \[ 4 = x^2 - 4x - 41 \]

  3. Rearrange the equation: \[ x^2 - 4x - 41 - 4 = 0 \ x^2 - 4x - 45 = 0 \]

  4. Factor the quadratic equation: \[ (x - 9)(x + 5) = 0 \]

  5. Therefore, we find the solutions: \[ x - 9 = 0 \quad \Rightarrow \quad x = 9 \ x + 5 = 0 \quad \Rightarrow \quad x = -5 \]

  6. Now, substitute these values back into \( y = 4 \):

    • For \( x = 9 \), \( (9, 4) \)
    • For \( x = -5 \), \( (-5, 4) \)

Thus, the solution to the system is: \[ (9, 4) \text{ and } (-5, 4) \]

The correct response is: (−5, 4) and (9, 4).