Q. \(x^{2}+2x-63=0\)

Answer

We solve the quadratic \(x^2+2x-63=0\) by factoring.

Find two numbers that multiply to \(-63\) and add to \(2\): \(9\) and \(-7\).

\[
x^2+2x-63=(x+9)(x-7)=0
\]

So \(x+9=0\) or \(x-7=0\).

\[
x=-9 \quad \text{or} \quad x=7
\]

Final result: \(x=7\) or \(x=-9\).

Detailed Explanation

We want to solve the quadratic equation:

\[
x^2 + 2x – 63 = 0
\]

Step 1: Factor the quadratic.

A quadratic of the form \(ax^2 + bx + c\) can be factored if we find two numbers whose product is \(ac\) and whose sum is \(b\).

Here, \(a = 1\), \(b = 2\), and \(c = -63\).

So we need two numbers \(m\) and \(n\) such that:

\[
m \cdot n = -63
\]
\[
m + n = 2
\]

Step 2: Find the numbers.

Because the product is \(-63\), one number must be positive and the other negative.

Check factor pairs of \(63\): \(1\) and \(63\), \(3\) and \(21\).

We test which pair gives a sum of \(2\):

\[
(-1) + 3 = 2
\]

So we take \(m = 3\) and \(n = -1\). Their product is:

\[
3 \cdot (-1) = -3
\]

That is not \(-63\), so we must use the factor pair method more carefully: we need factors that multiply to \(-63\) and add to \(2\).

Try these factor pairs of \(-63\):

\(63\) and \(-1\):

\[
63 + (-1) = 62 \quad \text{not } 2
\]

\(21\) and \(-3\):

\[
21 + (-3) = 18 \quad \text{not } 2
\]

\(9\) and \(-7\):

\[
9 + (-7) = 2
\]

Great! So the two numbers are \(9\) and \(-7\).

Step 3: Rewrite and factor the quadratic.

Now factor the expression:

\[
x^2 + 2x – 63 = (x+9)(x-7)
\]

Step 4: Set each factor equal to zero.

Using the zero product property:

\[
(x+9)(x-7)=0
\]
\[
x+9=0 \quad \text{or} \quad x-7=0
\]

Step 5: Solve each equation.

First equation:

\[
x+9=0
\]
\[
x=-9
\]

Second equation:

\[
x-7=0
\]
\[
x=7
\]

Final Answer:

The solutions to \(x^2 + 2x – 63 = 0\) are:

\[
x = -9 \quad \text{and} \quad x = 7
\]

See full solution

Graph

image
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Algebra FAQ

How do you solve \(x^2+2x-63=0\) by factoring?

Find two numbers with product \(-63\) and sum \(2\): \(9\) and \(-7\). So \(x^2+2x-63=(x+9)(x-7)=0\). Thus \(x=-9\) or \(x=7\).

What is the quadratic formula for \(x^2+2x-63=0\), and what are the solutions?

Use \(x=\frac{-b\pm\sqrt{b^2-4ac}}{2a}\) with \(a=1\), \(b=2\), \(c=-63\). Then \(x=\frac{-2\pm\sqrt{4+252}}{2}=\frac{-2\pm\sqrt{256}}{2}=\frac{-2\pm16}{2}\). So \(x=7\) or \(x=-9\).

What are the discriminant \(\Delta\) and what do they imply?

\(\Delta=b^2-4ac=2^2-4(1)(-63)=4+252=256\). Since \(\Delta>0\), there are two distinct real solutions. From \(\sqrt{\Delta}=16\), solutions are \(x=7\) and \(x=-9\).

How do you complete the square to solve \(x^2+2x-63=0\)?

Rewrite as \(x^2+2x=63\). Add \((1)^2\): \(x^2+2x+1=64\). Then \((x+1)^2=64\). So \(x+1=\pm8\), giving \(x=7\) or \(x=-9\).

How can you check the solutions quickly?

Substitute \(x=7\): \(49+14-63=0\). Substitute \(x=-9\): \(81-18-63=0\). Both satisfy the equation, so the solutions are correct.

Does the graph of \(y=x^2+2x-63\) intersect the \(x\)-axis at these points?

Yes. The zeros occur at \(x=-9\) and \(x=7\). Since the parabola opens upward, it crosses the \(x\)-axis at those two values and is positive outside them.
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