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Find the value or values of [tex]p[/tex] in the quadratic equation [tex]p^2 + 13p - 30 = 0[/tex].

A. [tex]p = 15, p = 2[/tex]

B. [tex]p = 10, p = 3[/tex]

C. [tex]p = -10, p = -3[/tex]

D. [tex]p = -15, p = 2[/tex]

Sagot :

Let's solve the quadratic equation [tex]\( p^2 + 13p - 30 = 0 \)[/tex] to find the values of [tex]\( p \)[/tex].

1. Identify the quadratic equation in standard form:
The given equation [tex]\( p^2 + 13p - 30 = 0 \)[/tex] is already in standard form [tex]\( ax^2 + bx + c = 0 \)[/tex] where:
[tex]\[ a = 1, \quad b = 13, \quad c = -30 \][/tex]

2. Use the quadratic formula:
The quadratic formula is:
[tex]\[ p = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a} \][/tex]
Here, [tex]\( a = 1 \)[/tex], [tex]\( b = 13 \)[/tex], and [tex]\( c = -30 \)[/tex]. Substituting these values into the formula gives:
[tex]\[ p = \frac{-13 \pm \sqrt{13^2 - 4 \cdot 1 \cdot (-30)}}{2 \cdot 1} \][/tex]

3. Calculate the discriminant:
The discriminant is [tex]\( b^2 - 4ac \)[/tex]:
[tex]\[ 13^2 - 4 \cdot 1 \cdot (-30) = 169 + 120 = 289 \][/tex]

4. Simplify under the square root:
[tex]\[ \sqrt{289} = 17 \][/tex]

5. Substitute back into the quadratic formula:
[tex]\[ p = \frac{-13 \pm 17}{2} \][/tex]

6. Solve for the two values of [tex]\( p \)[/tex]:

- For the [tex]\( + \)[/tex] part:
[tex]\[ p = \frac{-13 + 17}{2} = \frac{4}{2} = 2 \][/tex]

- For the [tex]\( - \)[/tex] part:
[tex]\[ p = \frac{-13 - 17}{2} = \frac{-30}{2} = -15 \][/tex]

So, the solutions to the equation [tex]\( p^2 + 13p - 30 = 0 \)[/tex] are [tex]\( p = -15 \)[/tex] and [tex]\( p = 2 \)[/tex].

Therefore, the best answer is:
D. [tex]\( p = -15, p = 2 \)[/tex]