Q. \(x^2 + 2x + 5 = 0\)
Answer
Solve \(x^2+2x+5=0\) using the quadratic formula \(x=\frac{-b\pm\sqrt{b^2-4ac}}{2a}\) with \(a=1\), \(b=2\), \(c=5\).
\[
\Delta=b^2-4ac=2^2-4(1)(5)=4-20=-16
\]
\[
x=\frac{-2\pm\sqrt{-16}}{2}=\frac{-2\pm 4i}{2}=-1\pm 2i
\]
Final answer: \(x=-1+2i\) or \(x=-1-2i\).
Detailed Explanation
We want to solve the equation
\[
x^2 + 2x + 5 = 0.
\]
Step 1: Identify the coefficients.
Compare with the standard quadratic form
\[
ax^2 + bx + c = 0.
\]
Here:
\[
a = 1,\quad b = 2,\quad c = 5.
\]
Step 2: Use the quadratic formula.
The solutions to \(ax^2 + bx + c = 0\) are given by
\[
x = \frac{-b \pm \sqrt{b^2 – 4ac}}{2a}.
\]
Step 3: Substitute \(a\), \(b\), and \(c\).
\[
x = \frac{-2 \pm \sqrt{2^2 – 4(1)(5)}}{2(1)}.
\]
Step 4: Simplify inside the square root (the discriminant).
Compute \(b^2 – 4ac\):
\[
2^2 – 4(1)(5) = 4 – 20 = -16.
\]
Step 5: Substitute the discriminant back in.
\[
x = \frac{-2 \pm \sqrt{-16}}{2}.
\]
Step 6: Simplify the square root of a negative number.
Since \(-16 = 16(-1)\), we have
\[
\sqrt{-16} = \sqrt{16}\sqrt{-1} = 4i,
\]
where \(i\) is the imaginary unit with \(i^2 = -1\).
Step 7: Final simplification.
\[
x = \frac{-2 \pm 4i}{2}.
\]
Split the division:
\[
x = \frac{-2}{2} \pm \frac{4i}{2}.
\]
\[
x = -1 \pm 2i.
\]
So the solutions are:
\[
\boxed{x = -1 + 2i \quad \text{and} \quad x = -1 – 2i.}
\]
Algebra FAQ
How do I solve \(x^2+2x+5=0\) using the quadratic formula?
What is the discriminant of \(x^2+2x+5=0\)? And what does it tell me?
Can I solve \(x^2+2x+5=0\) by completing the square?
What are the real solutions to \(x^2+2x+5=0\)?
Are the solutions complex numbers? What is their form?
How can I verify the roots \(x=-1\pm 2i\) work in the equation?
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