Determine whether the graphs of the equations are parallel, perpendicular, or neither.

[tex]\[
\begin{array}{l}
x + y = 3 \\
x - y = -3
\end{array}
\][/tex]

A. parallel
B. perpendicular
C. neither



Answer :

To determine whether the given lines are parallel, perpendicular, or neither, we need to find the slopes of each line.

Starting with the first equation:
[tex]\[ x + y = 3 \][/tex]

To express this in slope-intercept form [tex]\( y = mx + b \)[/tex]:
[tex]\[ y = -x + 3 \][/tex]
Here, [tex]\( m_1 = -1 \)[/tex] is the slope of the first line.

Now, consider the second equation:
[tex]\[ x - y = -3 \][/tex]

Rewriting this in slope-intercept form [tex]\( y = mx + b \)[/tex]:
[tex]\[ -y = -x - 3 \][/tex]
Multiplying both sides by -1 to solve for [tex]\( y \)[/tex]:
[tex]\[ y = x + 3 \][/tex]
Here, [tex]\( m_2 = 1 \)[/tex] is the slope of the second line.

With the slopes [tex]\( m_1 = -1 \)[/tex] and [tex]\( m_2 = 1 \)[/tex], we can now determine their relationship:

1. Parallel Lines: If the slopes are equal. That is, [tex]\( m_1 = m_2 \)[/tex].
2. Perpendicular Lines: If the product of the slopes is [tex]\(-1\)[/tex]. That is, [tex]\( m_1 \times m_2 = -1 \)[/tex].
3. Neither: If the slopes do not satisfy either condition above.

Calculating the product of the slopes:
[tex]\[ m_1 \times m_2 = (-1) \times 1 = -1 \][/tex]

Since the product of the slopes [tex]\((-1) \times 1 = -1\)[/tex], the lines are perpendicular.

Hence, the correct answer is:
B. perpendicular

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