Q. \(x^2 – 3x – 10 = 0\)

Answer

We solve the quadratic \(x^2-3x-10=0\) by factoring. Find two numbers that multiply to \(-10\) and add to \(-3\): \(2\) and \(-5\).

So, \((x-5)(x+2)=0\).

Thus \(x-5=0\) gives \(x=5\), and \(x+2=0\) gives \(x=-2\).

Final Result: \(\,x=5\) or \(\,x=-2\).

Detailed Explanation

We want to solve the equation

\[x^2 – 3x – 10 = 0.\]

Step 1: Identify the quadratic form

A quadratic equation has the form

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

Here, we can match coefficients:

\[a = 1,\quad b = -3,\quad c = -10.\]

Step 2: Factor the quadratic

The goal is to rewrite \(x^2 – 3x – 10\) as a product of two binomials:

\[(x + m)(x + n) = x^2 + (m+n)x + mn.\]

We need \(m+n = -3\) and \(mn = -10\).

Now list factor pairs of \(-10\):

  • \(1 \cdot -10 = -10\)
  • \(-1 \cdot 10 = -10\)
  • \(2 \cdot -5 = -10\)
  • \(-2 \cdot 5 = -10\)

Check which pair adds to \(-3\):

  • \(2 + (-5) = -3\) ✓

So \(m = 2\) and \(n = -5\). Therefore,

\[x^2 – 3x – 10 = (x + 2)(x – 5).\]

Step 3: Use the zero product property

If a product is zero, then at least one factor must be zero. So:

\[(x + 2)(x – 5) = 0.\]

This gives two equations:

\[x + 2 = 0 \quad \text{or} \quad x – 5 = 0.\]

Step 4: Solve each linear equation

First:

\[x + 2 = 0.\]

Subtract \(2\) from both sides:

\[x = -2.\]

Second:

\[x – 5 = 0.\]

Add \(5\) to both sides:

\[x = 5.\]

Final Answer

The solutions to the equation \(x^2 – 3x – 10 = 0\) are:

\[x = -2 \quad \text{or} \quad x = 5.\]

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Algebra FAQ

Solve \(x^2-3x-10=0\) using the quadratic formula.

\(x=\dfrac{3\pm\sqrt{(-3)^2-4(1)(-10)}}{2}=\dfrac{3\pm\sqrt{49}}{2}=\dfrac{3\pm 7}{2}\), so \(x=5\) or \(x=-2\).

Can the quadratic be factored?

\(x^2-3x-10=(x-5)(x+2)\). Setting each factor to zero gives \(x=5\) or \(x=-2\).

What is the discriminant \(b^2-4ac\) and what does it imply?

Here \(a=1,b=-3,c=-10\). Discriminant \(=9-4(1)(-10)=49>0\), so there are two real distinct roots: \(5\) and \(-2\).

How do you verify the solutions in the original equation?

For \(x=5\): \(25-15-10=0\). For \(x=-2\): \(4+6-10=0\). Both satisfy \(x^2-3x-10=0\).

What is the sum and product of the roots?

Sum \(= -\dfrac{b}{a}=\dfrac{3}{1}=3\). Product \(=\dfrac{c}{a}=-10\). Roots \(5\) and \(-2\) match: \(5+(-2)=3\), \(5(-2)=-10\).
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