Recent content by quadreg

  1. Q

    Prove algebraically that lim x->0 (x^2)*cos(1/ x^(1/3)) does not exist

    Out of curiosity is it possible for there to be more than one limit, given there's more than one root, whether the limit exists or not.
  2. Q

    Prove algebraically that lim x->0 (x^2)*cos(1/ x^(1/3)) does not exist

    Isn't the domain of x^{1/3} , include all ℝ, you can take the cube root of a negative can't you. eg. \sqrt[3]{-125}=-5
  3. Q

    Prove algebraically that lim x->0 (x^2)*cos(1/ x^(1/3)) does not exist

    so I get −1≤cos(\frac{1}{\sqrt[3]{x}})≤1 −x^{2}≤x^{2}cos(\frac{1}{\sqrt[3]{x}})≤x^{2} so as x -> 0 bounds -> 0, so the limit is 0. however wolfram alpha tells me otherwise...
  4. Q

    Prove algebraically that lim x->0 (x^2)*cos(1/ x^(1/3)) does not exist

    is it sometimes referred to as the squeeze theorem
  5. Q

    Prove algebraically that lim x->0 (x^2)*cos(1/ x^(1/3)) does not exist

    Even when I try to show that the limits are different either side of zero I keep getting divisions by zero.
  6. Q

    Prove algebraically that lim x->0 (x^2)*cos(1/ x^(1/3)) does not exist

    Homework Statement Prove algebraically that lim x->0 (x^2)*cos(1/ x^(1/3)) does not exist Homework Equations lim x->0 (x^2)*cos(1/ x^(1/3)) The Attempt at a Solution I know the limit does not exist but can't prove it algebraically.
  7. Q

    Prove f(x) = x^3 + 3^x is a one-to-one function.

    Ohh, that makes sense. 3x^2 is always >=0 and (3^x)ln3 is always >=0, so f'(x)>0. Thankyou.
  8. Q

    Prove f(x) = x^3 + 3^x is a one-to-one function.

    Yes, I tried solving for critical points, but i get f'(x)=3x^2+(3^x)ln3 and can't solve for x where f'(x) = 0
  9. Q

    Prove f(x) = x^3 + 3^x is a one-to-one function.

    Two x values give the same y value. Are you suggesting I use the horizontal line test?
  10. Q

    Prove f(x) = x^3 + 3^x is a one-to-one function.

    Homework Statement Prove f(x) = x^3 + 3^x is a one-to-one function. 2. The attempt at a solution Sum of one-to-one functions is a one-to-one function (I think/dont know how to prove). x^3 is one-to-one, 3^x is one-to-one, thus f(x) is one-to-one. Surely there's a more rigorous proof.