Use the quadratic formula to solve the quadratic equation 2x2−9x+11=0

2
𝑥
2

9
𝑥
+
11
=
0
.

Express its solutions in the form a±bi
𝑎
±
𝑏
𝑖

1 answer

To solve the quadratic equation \( 2x^2 - 9x + 11 = 0 \) using the quadratic formula, we start with the formula:

\[ x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a} \]

In your equation, the coefficients are:

  • \( a = 2 \)
  • \( b = -9 \)
  • \( c = 11 \)

First, we calculate the discriminant \( b^2 - 4ac \):

\[ b^2 = (-9)^2 = 81 \] \[ 4ac = 4 \cdot 2 \cdot 11 = 88 \] \[ b^2 - 4ac = 81 - 88 = -7 \]

Since the discriminant is negative (\(-7\)), the solutions will involve complex numbers. Now, we can substitute the values into the quadratic formula:

\[ x = \frac{-(-9) \pm \sqrt{-7}}{2 \cdot 2} \] \[ x = \frac{9 \pm \sqrt{-7}}{4} \]

We can express \(\sqrt{-7}\) as \(i\sqrt{7}\):

\[ x = \frac{9 \pm i\sqrt{7}}{4} \]

This can be separated into real and imaginary parts:

\[ x = \frac{9}{4} \pm \frac{\sqrt{7}}{4}i \]

Thus, the solutions are:

\[ x = \frac{9}{4} + \frac{\sqrt{7}}{4}i \quad \text{and} \quad x = \frac{9}{4} - \frac{\sqrt{7}}{4}i \]

In summary, the solutions expressed in the form \( a \pm bi \) are:

\[ \frac{9}{4} \pm \frac{\sqrt{7}}{4}i \]