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sha0403 Group Title

find an equation of the normal line to the parabola y=x^2-8x+9 at point (3,-6)... help me..

  • one year ago
  • one year ago

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  1. LogicalApple Group Title
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    Can you use calculus?

    • one year ago
  2. sha0403 Group Title
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    how to use it? i don't know coz it do not give the value of x after differetiate.. so i don't know how to find m..

    • one year ago
  3. LogicalApple Group Title
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    What do you get for y'(x) in general?

    • one year ago
  4. sha0403 Group Title
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    i get 2x -8...

    • one year ago
  5. LogicalApple Group Title
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    Perfect. This is the equation of the tangents of x^2 - 8x + 9. Let x = 3 and solve for y'(x) to get the tangent at that point.

    • one year ago
  6. LogicalApple Group Title
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    More specifically, y'(x) gives you the 'slope' of the tangent at x.

    • one year ago
  7. sha0403 Group Title
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    so after that if i get the value of m,, should i substitute the (3,-6) again tu find c?

    • one year ago
  8. LogicalApple Group Title
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    Let's assume you found the slope at x = 3. This is the slope of the tangent line. The slope of the normal line would be perpendicular to it. What is the relationship of slopes between perpendicular lines?

    • one year ago
  9. sha0403 Group Title
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    so, it share the same value of x? right?

    • one year ago
  10. LogicalApple Group Title
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    Well, the point (3, -6) will be the same. The only difference is, the slope of the normal line will be the negative reciprocal of the slope of the tangent line (since they are perpendicular).

    • one year ago
  11. LogicalApple Group Title
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    |dw:1356835091005:dw|

    • one year ago
  12. LogicalApple Group Title
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    The point there is supposed to represent (3, -6). The tangent line is drawn with a slope of m = y'(3), and the normal line is also drawn perpendicular to it.

    • one year ago
  13. sha0403 Group Title
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    ok i understand now...thanks for your explanation....

    • one year ago
  14. LogicalApple Group Title
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    y'(3) = 2(3) - 8 = -2 = slope of the tangent line Thus the slope of the normal line would be 1/2 and pass through (3, -6).

    • one year ago
  15. sha0403 Group Title
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    but i little bit confuse,, how do u know the shape of graph was perpendicular?

    • one year ago
  16. LogicalApple Group Title
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    Do you mean the direction of the normal line? A normal line is just a line perpendicular to whatever shape we're talking about. More specifically, a normal line is perpendicular to a tangent line.

    • one year ago
  17. sha0403 Group Title
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    ok i understand..thank u,, :)

    • one year ago
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