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zaphod

  • 3 years ago

Find the equation of the normal to the curve y = 3x^2-2x-1 which parellel to the line y = x-3

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  1. zaphod
    • 3 years ago
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    @sauravshakya @TuringTest @satellite73

  2. Algebraic!
    • 3 years ago
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    find y', set it equal to -1 and solve for x; that's an x coord. on your line. plug into y = 3x^2-2x-1to get a y coord. you have a point and the slope now.. find the line?

  3. myko
    • 3 years ago
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    1º. Find the derivative of y 2º Put it in some form you like (slope intercept, general...) 3º change it's direction vector to perpendicular 4º find x, for which it's slope is 1

  4. zaphod
    • 3 years ago
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    i got the points, why is the slope 1, it has to be -1 since we take the normal line?

  5. Algebraic!
    • 3 years ago
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    if slope of the tangent = -1, slope of the normal =1.

  6. zaphod
    • 3 years ago
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    can u show it in a diagram?

  7. Algebraic!
    • 3 years ago
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    |dw:1347988256856:dw|

  8. zaphod
    • 3 years ago
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    i cant picture the problem clearly?

  9. zaphod
    • 3 years ago
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    @Algebraic! where the parellel like y=x-3?

  10. Algebraic!
    • 3 years ago
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    wut

  11. zaphod
    • 3 years ago
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    can u show the parellel line y =x-3 in the diagram?

  12. Algebraic!
    • 3 years ago
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    |dw:1347988441351:dw|

  13. Algebraic!
    • 3 years ago
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    this was just a general sketch to illustrate the point. this isn't your parabola. but that's the line x-3 in black

  14. zaphod
    • 3 years ago
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    why cant we directly get the gradient as m=1 instead of -1

  15. Algebraic!
    • 3 years ago
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    try it and see

  16. zaphod
    • 3 years ago
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    im getting a different answer and the answer is wrong

  17. Algebraic!
    • 3 years ago
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    what's your answer?

  18. zaphod
    • 3 years ago
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    4y =2x-5

  19. zaphod
    • 3 years ago
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    dy/dx= 6x - 2 6x - 2 = 1 x= 1/2 y= -5/4

  20. zaphod
    • 3 years ago
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    cn u shw the working

  21. Algebraic!
    • 3 years ago
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    find y', set it equal to -1 and solve for x; that's an x coord. on your line. plug into y = 3x^2-2x-1to get a y coord. you have a point and the slope now.. find the line?

  22. zaphod
    • 3 years ago
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    why do we set it equal to -1 instead of 1?

  23. Algebraic!
    • 3 years ago
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    you don't like negative one so you went with one instead? and got the wrong answer?

  24. Algebraic!
    • 3 years ago
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    when the tangent to the parabola has a slope of -1, the normal at that point has a slope of 1

  25. zaphod
    • 3 years ago
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    i got it thanks :)

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