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Given the equations of two lines, [tex]\(5x - 3y = -2\)[/tex] and [tex]\(x - 3ky + 7 = 0\)[/tex], what could be the value of [tex]\(k\)[/tex] so that the two lines are perpendicular?

A) [tex]\(\frac{6}{15}\)[/tex]
B) [tex]\(\frac{1}{4}\)[/tex]
C) [tex]\(\frac{9}{10}\)[/tex]
D) [tex]\(-\frac{10}{10}\)[/tex]


Sagot :

Certainly! To determine the value of [tex]\(k\)[/tex] so that the two lines given by the equations [tex]\(5x - 3y = -2\)[/tex] and [tex]\(x - 3ky + 7 = 0\)[/tex] are perpendicular, we can follow these steps:

1. Convert the equations to slope-intercept form (y = mx + b):
- For the first line [tex]\(5x - 3y = -2\)[/tex], we solve for [tex]\(y\)[/tex]:
[tex]\[ 5x - 3y = -2 \implies -3y = -5x - 2 \implies y = \frac{5}{3}x + \frac{2}{3} \][/tex]
Therefore, the slope of the first line, [tex]\(m_1\)[/tex], is [tex]\(\frac{5}{3}\)[/tex].

- For the second line [tex]\(x - 3ky + 7 = 0\)[/tex], we solve for [tex]\(y\)[/tex]:
[tex]\[ x - 3ky + 7 = 0 \implies -3ky = -x - 7 \implies y = \frac{1}{3k}x + \frac{7}{3k} \][/tex]
Therefore, the slope of the second line, [tex]\(m_2\)[/tex], is [tex]\(\frac{1}{3k}\)[/tex].

2. Use the condition for perpendicular lines:
- Two lines are perpendicular if the product of their slopes is [tex]\(-1\)[/tex]:
[tex]\[ m_1 \cdot m_2 = -1 \][/tex]
Substituting the slopes from above, we get:
[tex]\[ \left(\frac{5}{3}\right) \cdot \left(\frac{1}{3k}\right) = -1 \][/tex]
Simplify this equation:
[tex]\[ \frac{5}{3} \cdot \frac{1}{3k} = -1 \implies \frac{5}{9k} = -1 \][/tex]

3. Solve for [tex]\(k\)[/tex]:
- To find [tex]\(k\)[/tex], we solve the equation:
[tex]\[ \frac{5}{9k} = -1 \implies 5 = -9k \implies k = -\frac{5}{9} \][/tex]

Therefore, the value of [tex]\(k\)[/tex] that makes the two lines perpendicular is:

[tex]\[ \boxed{-\frac{5}{9}} \][/tex]