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Type: Posts; User: Elisha Grey

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  1. Answers
    7
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    4,148

    0 + 0. Now...

    0 <= -x**2 -3x - 70, so x**2 + 3x + 70 >+ 0. Now the discriminate of this quadratic is negative, so it has no real root. Hence it is either always >+ 0 or always <= 0. Since it it >= 0 when x = 0,...
  2. Answers
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    2,792

    As Capuchin says, divide the first equation by 3...

    As Capuchin says, divide the first equation by 3 to get
    x + 2y = -2. And the second equation is
    5x - 2y = 14. Add these two equations to get
    6x = 12, so x = 2,and fro the first equation we have...
  3. Answers
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    4,260

    h(-4) = -1/3(-(-4)+5) = -1/3(9) = -3 gh(4) =...

    h(-4) = -1/3(-(-4)+5) = -1/3(9) = -3
    gh(4) = g(-3) = (4(-3)+4)5 = (-8)5 = -40
  4. Answers
    2
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    738

    Of course g(4)=g(4), As Adam is the same as Adam....

    Of course g(4)=g(4), As Adam is the same as Adam. What do you mean by the inverse of this?
  5. Answers
    2
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    983

    f(g(x)) = g(x)^2 - 3 = (-1 - x)^2 - 3 = 1 + 2x +...

    f(g(x)) = g(x)^2 - 3 = (-1 - x)^2 - 3 = 1 + 2x + x^2 - 3 =
    x^2 + 2x - 2
  6. Answers
    3
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    514

    This is not a composite function. If you are...

    This is not a composite function. If you are asking about
    f(g(x)) = 7g(x) + 49 = 7(x + 3) + 49 = 7x + 70 or
    g(f(x)) = f(x) + 3 = (7x + 49) + 3 = 7x + 52,
    in either case the domain is the...
  7. Answers
    18
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    1,897

    That post I made in answer to the question was a...

    That post I made in answer to the question was a year ago. Step by step is in the post. If you have any problemms with this post let me know and I'll try to clarify it.
  8. Answers
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    3,818

    I'm with you, Oranges!

    I'm with you, Oranges!
  9. Answers
    3
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    1,054

    52

    52<n+26, so (subtracting 26 from both sides) 26<n
  10. Question: Inequalities

    by Elisha Grey
    Answers
    7
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    1,699

    Cost is at loelast $60.

    Cost is at loelast $60.
  11. Answers
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    2,725

    I'm only answering the questions that have been...

    I'm only answering the questions that have been incorrectly answered before. In this question outward bound the pilot flies 600 mph for 1 hour and travels 600 * 1 = 600 miles; inward bound he...
  12. Answers
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    2,725

    out rate = 600 mph, in rate = 400 mph, total time...

    out rate = 600 mph, in rate = 400 mph, total time = time = 2 hours, 30 min = 2 1/2 hours = 5/2 hours. If he flies outbound for t hours, his outbound distance is 600t and his inbound distance is...
  13. Answers
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    1,668

    Volume = V = pi * r^2 * h, so h = V/(pi * r^2)....

    Volume = V = pi * r^2 * h, so h = V/(pi * r^2).
    Ssurface area = S = 2 * pi * r^2 + 2 * pi * r * h = 2 * pi * r^2 + 2 * pi * r * V / (pi * r^2)
    = 2 * pi * r^2 + 2 * V / r....
  14. Question: Algebra

    by Elisha Grey
    Answers
    7
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    1,832

    4^(1/3) + 4^(1/4) = 4^((1/3) +1/4)) = 4^(7/12) =...

    4^(1/3) + 4^(1/4) = 4^((1/3) +1/4)) = 4^(7/12) = (2^2)^7/12) =2^(2*(7/12)) = 2^(7/6)
  15. Answers
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    2,210

    1 is a quarter of 4

    1 is a quarter of 4
  16. Answers
    2
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    751

    There are four such points, with coordinates...

    There are four such points, with coordinates ((+-)sqrt6,(+-)sqrt6)
  17. Answers
    3
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    1,714

    z = 3 + I = sqrt (10) e^(I arc tan(1/3)) =...

    z = 3 + I = sqrt (10) e^(I arc tan(1/3)) = 10^(1/2) e^(I arc tan(1/3)), so sqrt z =
    10^(1/4) e^(I(1/2)arc tan(1/3)).
  18. Answers
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    5,720

    d/dx(sinx/x) = (sin x - x cos x)/x^2 < 0 iff sin...

    d/dx(sinx/x) = (sin x - x cos x)/x^2 < 0 iff sin x - x cox s < 0 iff sin x < x cos x iff tan x < x, which is not true in this range. In fact the opposite is true: tanx >= x in this range, so sin...
  19. Question: Factoring

    by Elisha Grey
    Answers
    2
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    958

    If you mean x^3 - 2x^2 - 4x + 8, then this equals...

    If you mean x^3 - 2x^2 - 4x + 8, then this equals
    x^2(x-2) - 4(x-2) = (x^2 - 4) (x-2) = (x+2)(x-2)^2
  20. Question: Probability

    by Elisha Grey
    Answers
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    1,850

    (a) The probability of getting no 1 is (5/6)^3,...

    (a) The probability of getting no 1 is (5/6)^3, so the probability of getting at least one 1 is
    1 - (5/6)^3

    (b) The probability of getting a 1 on one particular die and not a 1 on the other two...
  21. Answers
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    3,818

    Speaking of tricks there is one that I find...

    Speaking of tricks there is one that I find helpful in checking my arithmetic. It's caslled "casting out 9's" and it seems to be becoming lost.

    What it is is that in any arithmetic operation you...
  22. Answers
    18
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    1,897

    The tangent line is vertical when the denominator...

    The tangent line is vertical when the denominator of dy/dx = (3x**2 y ? y**2)/(2xy -x**3) is zero. i.e. when 0 = 2xy - x**3 = x(2y-x**2). This happens when x=0 or when y = x**2/2. In this case 6 =...
  23. Question: C 90 Cassette

    by Elisha Grey
    Answers
    2
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    903

    Such a relation is surely not linear, depending...

    Such a relation is surely not linear, depending on the thickness of the tape, what the counter is really measuring, etc. Your best bet (I've actually done this) is to let the tape run and record the...
  24. Answers
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    1,061

    The trouble with your solution for A is, is the...

    The trouble with your solution for A is, is the resulting sequence bounded?

    As for B, there is no increasing bounded sequence of natural numbers. This is because, if a sequence is bounded, say by...
  25. Answers
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    1,584

    (x/y)**4 (y/x)**4 (8x7x6x5)/(4x3x2x1) = 70

    (x/y)**4 (y/x)**4 (8x7x6x5)/(4x3x2x1) = 70
  26. Answers
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    3,818

    Speaking as a retired math teacher my advice...

    Speaking as a retired math teacher my advice would be as follows.

    I think it is a great mistake to try to understand math at an inappropriate level. Mathematics is different from most subject in...
  27. Answers
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    1,304

    at a point (x,y) we have 2(x-h) + 2(y-k)der of y...

    at a point (x,y) we have 2(x-h) + 2(y-k)der of y = 0, so der of y = -(x-h)/(y-k) = slope of a tangent line at this point. A radial line goes through (x,y) and (h,k), so its slope is (y-k)/(x-h),...
  28. Question: Simplify

    by Elisha Grey
    Answers
    6
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    5,924

    sqrt (4 - x**2) = sqrt (4 - (2 cos theta)**2) =...

    sqrt (4 - x**2) = sqrt (4 - (2 cos theta)**2) = sqrt (4 - 4 cos**2 theta) =
    sqrt (4 (1 - cos**2 theta)) = sqrt (2**2 sin**2 theta) = 2sin theta
  29. Answers
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    1,304

    log a 16 = log a 2**4 = 4 log a 2 = 4.. 4307 =...

    log a 16 = log a 2**4 = 4 log a 2 = 4.. 4307 = 1.7228
  30. Question: Trigonometry

    by Elisha Grey
    Answers
    1
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    1,375

    Calling the heighth of the tree x, the distance...

    Calling the heighth of the tree x, the distance to the first measurement y, the first angle a=36.7, and the second angle b=22.2, we have cot a=y/x, so y=x cot a. Also cot b = (y+50)/x = (x cot a +...
  31. Answers
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    1,563

    Convert text file for CD player

    Can I convert a text file--presumably ASCII--to a format I can burn to and played on an ordinary CD?
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