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CSmith17

Write the equation of a line which passes through (3,5) and is perpendicular to y=(3/4)x-6 in slope-intercept form.

  • 11 months ago
  • 11 months ago

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  1. e.mccormick
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    First, do you know the method to find the slope of a perpendicular line?

    • 11 months ago
  2. CSmith17
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    y=mx+b?

    • 11 months ago
  3. telijahmed
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    |dw:1369021818640:dw|

    • 11 months ago
  4. e.mccormick
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    Not in this case. The perpendicular is the negative inverse of the slope of the given line. Do you know what that is?

    • 11 months ago
  5. telijahmed
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    |dw:1369021841094:dw|

    • 11 months ago
  6. telijahmed
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    |dw:1369021901093:dw|

    • 11 months ago
  7. CSmith17
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    Oh ok i always get those two confused.

    • 11 months ago
  8. shamim
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    if slope of ur given line is \[m _{1}\]

    • 11 months ago
  9. e.mccormick
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    So, what would the slope of the perpendicular line be in this case?

    • 11 months ago
  10. shamim
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    then \[m _{1}=\frac{ 3 }{ 4 }\]

    • 11 months ago
  11. shamim
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    if the slope of a perpendicular line is \[m _{2}\]

    • 11 months ago
  12. CSmith17
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    Ok is the equation to find out what the perpendicular line y=mx+b or m=y^2 - y^1 / x^2-x^1?

    • 11 months ago
  13. shamim
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    then\[m _{1}m _{2}=-1\]

    • 11 months ago
  14. shamim
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    or\[\frac{ 3 }{ 4 }m _{2}=-1\]

    • 11 months ago
  15. e.mccormick
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    We need the slope first. shamim has pointed out the slope of the original line. Do you know what is meant by the "negative inverse" of that?

    • 11 months ago
  16. CSmith17
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    The negative opposite?

    • 11 months ago
  17. shamim
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    \[m _{2}=\frac{ -4 }{ 3 }\]

    • 11 months ago
  18. e.mccormick
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    Well, inverse is sort of opposite. If you mean inverse as in \(\frac{a}{b}\implies \frac{b}{a}\) is the inverse.

    • 11 months ago
  19. CSmith17
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    Alright, so in order to find the slope we use y=mx+b right?

    • 11 months ago
  20. e.mccormick
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    To invert is to turn upside down or reverse position. That is where inverse comes from. Just some simple language, but they make it sound cryptic by tossing it into math. No, shamim went ahead and posted it. All you needed was the m part of the original line. Do you see the \(m_2\)?

    • 11 months ago
  21. CSmith17
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    Yes, i see. So next up would be to use the y^2-y^1 equation?

    • 11 months ago
  22. e.mccormick
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    Yes.

    • 11 months ago
  23. CSmith17
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    So in this case (3,5) would be (x^1,y^1) while −4/3 would be (x^2,y^2)?

    • 11 months ago
  24. e.mccormick
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    No, -4/3 is m. You just need that and one point.

    • 11 months ago
  25. e.mccormick
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    \(y-y_1=m(x-x_1)\)

    • 11 months ago
  26. CSmith17
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    y-5 = -4/3(x-3) is that right so far?

    • 11 months ago
  27. e.mccormick
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    Yes!

    • 11 months ago
  28. CSmith17
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    And that would be the final answer correct?

    • 11 months ago
  29. e.mccormick
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    This became a bit of a posting mess and then the site went down, so here is a summary of what was done: You were given the line \(y=\frac{3}{4}x-6 \) and point \((3,5)\) with the instructions to find the slope-intercept equation of the perpendicular line through that point. First, you need the slope of the line being found. The perpendicular line has the negative inverse slope of the given line. To invert is to turn upside down or reverse position and negative is the mathematical changing of sign from \(+\) to \(-\) or \(-\) to \(+\). If you understand the concept, you flip it and make it the opposite sign. However, here is the mathematical way to find the slope of the perpendicular line: Start with the original line, \(y=\frac{3}{4}x-6 \). Form that you get \(m_1\). The negative inverse implies that if they were multiplied, the result would be -1. That is stated as: \(m_1m_2=-1\) and put what is known, \(m_1\) into that: \(\frac{3}{4}m_2=-1\) Then solve for \(m_2\) \(\frac{3}{4}m_2=-1\) \(\frac{4}{3}\cdot\frac{3}{4}m_2=\frac{4}{3}\cdot-1\) \(m_2=-\frac{4}{3}\) So \(m_2=-\frac{4}{3}\) becomes just m for the new formula, the point-slope version of a line. Point slope lets you use any point and the slope to find the formula of a line: \(y-y_1=m(x-x_1)\) \(y-y_1=-\frac{4}{3}(x-x_1)\) Then we toss in the point \((3,5)\): \(y-5=-\frac{4}{3}(x-3)\) That is a formula for the line, but they wanted a specific formula, the slope-intercept version. To get that, you need to solve for y. \(y-5=-\frac{4}{3}(x-3)\) \(y-5=-\frac{4}{3}x+4\) \(y-5+5=-\frac{4}{3}x+4+5\) \(y=-\frac{4}{3}x+9\) And there it is! The slope-intercept equation of the perpendicular line through the given point.

    • 11 months ago
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