Two Solutions for All Quadratic Equations Quick Check

5 of 55 of 5 Items
Question
Solve the quadratic equation 10x2−2x+13=3
. Which of the following expresses its solutions in the form a±bi
?(1 point)
Responses

−110±311√10i
negative Start Fraction 1 over 10 End Fraction plus or minus Start Fraction 3 Start Root 11 End Root over 10 End Fraction i

110±101√10i
Start Fraction 1 over 10 End Fraction plus or minus Start Fraction Start Root 101 End Root over 10 End Fraction i

15±311√5i
Start Fraction 1 over 5 End Fraction plus or minus Start Fraction 3 Start Root 11 End Root over 5 End Fraction i

110±311√10i

1 answer

To solve the quadratic equation \(10x^2 - 2x + 13 = 3\), we first move all terms to one side of the equation to set it to zero:

\[ 10x^2 - 2x + 13 - 3 = 0 \] This simplifies to:

\[ 10x^2 - 2x + 10 = 0 \]

Now, we can apply the quadratic formula:

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

Where \(a = 10\), \(b = -2\), and \(c = 10\). Plugging in the values, we first calculate \(b^2 - 4ac\):

\[ b^2 = (-2)^2 = 4 \] \[ 4ac = 4 \cdot 10 \cdot 10 = 400 \] \[ b^2 - 4ac = 4 - 400 = -396 \]

Since the discriminant is negative (\(-396\)), we will have complex solutions. Now substituting back into the quadratic formula:

\[ x = \frac{-(-2) \pm \sqrt{-396}}{2 \cdot 10} \] \[ x = \frac{2 \pm \sqrt{-396}}{20} \]

To express \(\sqrt{-396}\):

\[ \sqrt{-396} = \sqrt{396}i = \sqrt{4 \cdot 99}i = 2\sqrt{99}i = 2\sqrt{9 \cdot 11}i = 6\sqrt{11}i \]

Now substituting this back into the equation:

\[ x = \frac{2 \pm 6\sqrt{11}i}{20} = \frac{1 \pm 3\sqrt{11}i}{10} \]

Thus, the solutions can be expressed as:

\[ x = \frac{1}{10} \pm \frac{3\sqrt{11}}{10}i \]

Now, looking at the responses you provided, the correct one is:

Positive \(\frac{1}{10} \pm \frac{3\sqrt{11}}{10} i\).

This matches the format: \[ \frac{1}{10} \pm \frac{3\sqrt{11}}{10}i \]

So the response is:

Start Fraction 1 over 10 End Fraction plus or minus Start Fraction 3 Start Root 11 End Root over 10 End Fraction i.

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