IGCSEMathsEdexcelMaths AHigherFlashcardsNumbers & the Number SystemPowers, Roots & Standard Form

Powers, Roots & Standard Form (Edexcel IGCSE Maths A)

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  • FrontPowers & Roots

    What is a square root of a number?

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  • What is a square root of a number?

    A square root of a number is a value that, when squared, gives the original number.

    E.g. 3 is the square root of 9 because 32 = 3 x 3 = 9.

  • True or False?

    Every positive number has two square roots.

    True.

    Every positive number has two square roots, one positive and one negative.

    E.g. square root of 64 equals 8 and negative 8

  • True or False?

    Cube roots of negative numbers do not exist.

    False.

    The cube root of a negative number will also be a negative number.

    For example, -5 is a cube root of -125.

  • Define the term reciprocal.

    The reciprocal of a number is the number that you multiply it by to get 1.

    For example, 2 over 3 is the reciprocal of 3 over 2.

  • How do I estimate a root, e.g. the square root of 27?

    You can estimate the root of a number by finding the closest integer roots either side of it.

    E.g. To find square root of 27

    square root of 25 equals 5 and square root of 36 equals 6

    So square root of 27 is between 5 and 6

  • What number do you get when you raise any non-zero number to the power of zero, e.g. 20?

    Any non-zero number raised to the power of 0 is equal to 1.

    E.g. 20 = 1.

  • True or False?

    If you raise a non-zero number to the power of 1, you get 1.

    False.

    Any number raised to the power 1 is just itself.

    E.g. 6 to the power of 1 equals 6.

  • What do you get if you raise a non-zero number to the power of -1,
    e.g. 3-1 ?

    If you raise a non-zero number to the power of -1 you get the reciprocal of the number.

    E.g. 3 to the power of negative 1 end exponent equals 1 third.

  • What do you get if you raise a positive number to the power of ½,
    e.g. 51/2 ?

    If you raise a non-zero number to the power of ½ you get its positive square root.

    E.g. 5 to the power of 1 half end exponent equals square root of 5.

  • What is the index law for a to the power of m cross times a to the power of n?

    a to the power of m cross times a to the power of n equals a to the power of m plus n end exponent

    If you multiply two powers with the same base number, you add the indices together.

  • What is the index law for a to the power of m divided by a to the power of n?

    a to the power of m divided by a to the power of n equals a to the power of m minus n end exponent

    If you divide two powers with the same base number, you subtract one index from the other.

  • What is the index law for open parentheses a to the power of m close parentheses to the power of n?

    open parentheses a to the power of m close parentheses to the power of n equals a to the power of m cross times n end exponent

    If you raise a power to another power, you multiply the indices.

  • True or False?

    a to the power of m over n end exponent equals open parentheses m-th root of a to the power of n end root close parentheses

    False.

    a to the power of m over n end exponent equals open parentheses n-th root of a close parentheses to the power of m

    The denominator of an index is the root and the numerator of an index is the power.

  • What does a number written in standard form look like?

    A number in standard form looks like a cross times 10 to the power of n, e.g. 5.2 cross times 10 cubed.

    It is a number between 1 and 10 multiplied by a power of ten.

  • When a number is written in standard form a cross times 10 to the power of n, which values can a be?

    For a cross times 10 to the power of n, a is at least 1 and less than 10, 1 less or equal than a less than 10.

    This means there is one non-zero digit before the decimal point.

  • True or False?

    When a number is written in standard form a cross times 10 to the power of n, n can be a fraction.

    False.

    For a number written in standard form, a cross times 10 to the power of n, the value n must be an integer.

    It can be zero, positive or negative.

  • When a value between 0 and 1, is written in standard form a cross times 10 to the power of n, what type of number will n be?

    If a value is between 0 and 1 then when it is written in standard form, n will be a negative integer.

    E.g. 0.083 would be written as 8.3 x 10-2.

  • How do you multiply two numbers that are written in standard form and give the answer in standard form using index laws?

    E.g. open parentheses 2 cross times 10 cubed close parentheses cross times open parentheses 6 cross times 10 to the power of 5 close parentheses

    Multiply together the values of a from both numbers and write this in standard form if needed, e.g. 2 cross times 6 equals 12 equals 1.2 cross times 10 to the power of 1.

    Use index laws to combine the powers of 10, e.g. 10 cubed cross times 10 to the power of 5 equals 10 to the power of 8.

    Multiply the two parts together, e.g. 1.2 cross times 10 to the power of 1 cross times 10 to the power of 8.

    Simplify if necessary, using index laws again e.g. 1.2 cross times 10 to the power of 9.

  • How do you divide two numbers that are written in standard form and give the answer in standard form using index laws?

    E.g. open parentheses 2 cross times 10 to the power of 9 close parentheses divided by open parentheses 8 cross times 10 squared close parentheses

    Divide the values of a for both numbers and write this in standard form if needed, e.g. 2 divided by 8 equals 0.25 equals 2.5 cross times 10 to the power of negative 1 end exponent

    Combine the powers of 10 using index laws, e.g. 10 to the power of 9 divided by 10 squared equals 10 to the power of 7

    Multiply the two parts together, e.g. 2.5 cross times 10 to the power of negative 1 end exponent cross times 10 to the power of 7

    Simplify using index laws again if necessary, e.g. 2.5 cross times 10 to the power of 6

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