Powers and roots

  • Ab Surd Ity
    problem
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    Ab Surd Ity

    Age
    16 to 18
    Challenge level
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    Find the value of sqrt(2+sqrt3)-sqrt(2-sqrt3)and then of cuberoot(2+sqrt5)+cuberoot(2-sqrt5).
  • Absurdity Again
    problem

    Absurdity Again

    Age
    16 to 18
    Challenge level
    filled star empty star empty star
    What is the value of the integers a and b where sqrt(8-4sqrt3) = sqrt a - sqrt b?
  • Route to Root
    problem

    Route to Root

    Age
    16 to 18
    Challenge level
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    A sequence of numbers x1, x2, x3, ... starts with x1 = 2, and, if you know any term xn, you can find the next term xn+1 using the formula: xn+1 = (xn + 3/xn)/2 . Calculate the first six terms of this sequence. What do you notice? Calculate a few more terms and find the squares of the terms. Can you prove that the special property you notice about this sequence will apply to all the later terms of the sequence? Write down a formula to give an approximation to the cube root of a number and test it for the cube root of 3 and the cube root of 8. How many terms of the sequence do you have to take before you get the cube root of 8 correct to as many decimal places as your calculator will give? What happens when you try this method for fourth roots or fifth roots etc.?
  • How Many Solutions?
    problem
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    How Many Solutions?

    Age
    16 to 18
    Challenge level
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    Find all the solutions to the this equation.
  • Mod 7
    problem

    Mod 7

    Age
    16 to 18
    Challenge level
    filled star empty star empty star
    Find the remainder when 3^{2001} is divided by 7.
  • Staircase
    problem

    Staircase

    Age
    16 to 18
    Challenge level
    filled star empty star empty star
    Solving the equation x^3 = 3 is easy but what about solving equations with a 'staircase' of powers?
  • Like Powers
    problem

    Like Powers

    Age
    11 to 14
    Challenge level
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    Investigate $1^n + 19^n + 20^n + 51^n + 57^n + 80^n + 82^n $ and $2^n + 12^n + 31^n + 40^n + 69^n + 71^n + 85^n$ for different values of n.
  • Two Many
    problem

    Two Many

    Age
    11 to 14
    Challenge level
    filled star empty star empty star
    What is the least square number which commences with six two's?
  • Lost in Space
    problem

    Lost in Space

    Age
    14 to 16
    Challenge level
    filled star empty star empty star
    How many ways are there to count 1 - 2 - 3 in the array of triangular numbers? What happens with larger arrays? Can you predict for any size array?
  • Powers of Four
    problem

    Powers of Four

    Age
    14 to 16
    Challenge level
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    Can you work out the value of x in this 'power-full' equation?