Q. \(x^2 – x – 6 = 0\)

Answer

We solve \(x^2-x-6=0\) by factoring.

\(x^2-x-6=(x-3)(x+2)\), so

\((x-3)(x+2)=0 \Rightarrow x-3=0 \text{ or } x+2=0.\)

Thus \(x=3\) or \(x=-2\).

Final answer: \(x=3,\,-2\).

Detailed Explanation

We want to solve the equation

\[
x^2 – x – 6 = 0
\]

This is a quadratic equation, so we look for ways to factor it (or use the quadratic formula). Since it has nice integers, factoring is the fastest method.

Step 1: Identify the coefficients.

Compare

\[
x^2 – x – 6 = 0
\]

with the general form

\[
ax^2 + bx + c = 0
\]

Here:

  • \(a = 1\)
  • \(b = -1\)
  • \(c = -6\)

Step 2: Factor the quadratic.

Factor the expression \(x^2 – x – 6\) into two binomials of the form

\[
(x + m)(x + n)
\]

where \(m\) and \(n\) are integers.

For the product to match:

  • \(m \cdot n = -6\)
  • \(m + n = -1\) (because the middle term is \(-x\))

Step 3: Find integers that satisfy both conditions.

List factor pairs of \(-6\):

  • \(-1\) and \(6\) gives sum \(5\)
  • \(1\) and \(-6\) gives sum \(-5\)
  • \(-2\) and \(3\) gives sum \(1\)
  • \(2\) and \(-3\) gives sum \(-1\)

The pair \(2\) and \(-3\) works because:

  • \(2 \cdot (-3) = -6\)
  • \(2 + (-3) = -1\)

Step 4: Write the factored form.

\[
x^2 – x – 6 = (x + 2)(x – 3)
\]

Step 5: Set each factor equal to zero.

Since the product is zero:

\[
(x + 2)(x – 3) = 0
\]

we get two equations:

\[
x + 2 = 0
\]
\[
x – 3 = 0
\]

Step 6: Solve each equation.

From \(x + 2 = 0\):

\[
x = -2
\]

From \(x – 3 = 0\):

\[
x = 3
\]

Final Answer:

\[
x = -2 \quad \text{or} \quad x = 3
\]

See full solution

Graph

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Algebra FAQ

What are the solutions to \(x^2-x-6=0\)?

Factor: \((x-3)(x+2)=0\), so \(x=3\) or \(x=-2\).

How do you solve \(x^2-x-6=0\) by factoring?

Find two numbers with product \(-6\) and sum \(-1\): \(-3\) and \(2\). Then \(x^2-x-6=(x-3)(x+2)\).

How do you solve it using the quadratic formula?

For \(a=1,b=-1,c=-6\): \(x=\frac{-(-1)\pm\sqrt{(-1)^2-4(1)(-6)}}{2(1)}=\frac{1\pm\sqrt{25}}{2}=\frac{1\pm5}{2}\).

What is the discriminant of \(x^2-x-6=0\)?

\(D=b^2-4ac=(-1)^2-4(1)(-6)=1+24=25\).

How many real solutions does the equation have?

Since \(D=25>0\), there are \(2\) distinct real solutions.

What is the vertex of the parabola \(y=x^2-x-6\)?

Vertex at \(x=-\frac{b}{2a}=-\frac{-1}{2(1)}=\frac{1}{2}\). Then \(y=\left(\frac{1}{2}\right)^2-\frac{1}{2}-6=-\frac{25}{4}\).
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