Questions: Select the correct answer.
What are the solutions of the quadratic equation below?
2 x^2 - 2 x - 9 = 0
A. (-1 ± √19)/2
B. (3 ± √19)/2
C. (1 ± √19)/2
D. (1 ± 3√19)/2
Transcript text: Select the correct answer.
What are the solutions of the quadratic equation below?
\[
2 x^{2}-2 x-9=0
\]
A. $\frac{-1 \pm \sqrt{19}}{2}$
B. $\frac{3 \pm \sqrt{19}}{2}$
C. $\frac{1 \pm \sqrt{19}}{2}$
D. $\frac{1 \pm 3 \sqrt{19}}{2}$
Solution
Solution Steps
Step 1: Identify the coefficients
The quadratic equation is given as:
\[
2x^{2} - 2x - 9 = 0
\]
Here, the coefficients are:
\( a = 2 \)
\( b = -2 \)
\( c = -9 \)
Step 2: Apply the quadratic formula
The quadratic formula is:
\[
x = \frac{-b \pm \sqrt{b^{2} - 4ac}}{2a}
\]
Substitute the values of \( a \), \( b \), and \( c \) into the formula:
\[
x = \frac{-(-2) \pm \sqrt{(-2)^{2} - 4 \cdot 2 \cdot (-9)}}{2 \cdot 2}
\]
Step 3: Simplify the expression
Calculate the discriminant and simplify:
\[
x = \frac{2 \pm \sqrt{4 + 72}}{4}
\]
\[
x = \frac{2 \pm \sqrt{76}}{4}
\]
\[
x = \frac{2 \pm 2\sqrt{19}}{4}
\]
\[
x = \frac{1 \pm \sqrt{19}}{2}
\]
Final Answer
The correct answer is C. \( \boxed{\frac{1 \pm \sqrt{19}}{2}} \)