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Posted by on Friday, March 13, 2009 at 8:56pm.

f(x)=(5x-4)e^2x
How do you find the one critical number??

  • math-calc - , Friday, March 13, 2009 at 9:15pm

    Differentiate and put equal to zero.
    f'[x] = 5e^(2x) + 2e^(2x)(-4+5x)
    f'[0] = -3
    So the x-coordinate is -3

    I'd guess that that is what the question wants.

    Hope that helps

  • math-calc - , Friday, March 13, 2009 at 9:23pm

    I made a slight error. i don't want f'[0], i want f'[x] = 0 to find x = something.

    so we get 5e^(2x) + 2e^(2x)(-4+5x) = 0
    divide across by e^(2x)
    we get 5 + 2(-4+5x) = 0
    5 - 8 + 10x =0
    10x = 3
    x = 3/10
    Sorry about the mistake in my first post.

    hope that helps

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