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

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Express its solutions in the form a±bi
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1 answer

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

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

In our equation, the coefficients are:

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

Let's first calculate the discriminant \(b^2 - 4ac\):

\[ b^2 = (-9)^2 = 81 \] \[ 4ac = 4 \times 2 \times 11 = 88 \] \[ \text{Discriminant} = b^2 - 4ac = 81 - 88 = -7 \]

Since the discriminant is negative (\(-7\)), this means the solutions will involve imaginary numbers.

Next, we substitute the values into the quadratic formula:

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

Now, let's express \( \sqrt{-7} \) in terms of \(i\):

\[ \sqrt{-7} = i\sqrt{7} \]

Now we substitute this back into the formula:

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

We can separate this into real and imaginary parts:

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

Thus, the final solutions in the form \(a \pm bi\) are:

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

So, the solutions to the equation \(2x^2 - 9x + 11 = 0\) are:

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