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IB DP Maths AI SL Study Notes

1.1.2 Advanced Arithmetic

Powers

Powers, often referred to as exponents, signify the number of times a particular number is multiplied by itself.

  • Base: This is the number that is being multiplied.
  • Exponent: This number indicates how many times the base is used as a factor.

Understanding Powers

When we talk about powers, it's not just about multiplication. It's about understanding the growth and how numbers can exponentially increase or decrease.

For instance:

  • 23 means 2 is multiplied by itself two more times: 2 x 2 x 2 = 8
  • 54 means 5 is multiplied by itself three more times: 5 x 5 x 5 x 5 = 625

Negative Exponents

Numbers raised to negative exponents aren't about making the number smaller but rather taking its reciprocal and raising it to the positive exponent.

  • 2-3 doesn't mean the number becomes smaller. It means: 1/23 = 1/8

Zero Exponents

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

  • 70 = 1
  • 1230 = 1

Example Question 1

Calculate 45.

Solution: 45 = 4 x 4 x 4 x 4 x 4 = 1024

Roots

Roots, the inverse of powers, determine which number, when raised to a certain power, results in the given number.

Square Roots

The square root of a number identifies a value which, when multiplied by itself, returns the original number.

For example: √16 = 4 because 4 x 4 = 16

Cube Roots

The cube root of a number identifies a value which, when multiplied by itself twice, gives back the original number.

For instance: ∛64 = 4 because 4 x 4 x 4 = 64

Higher Roots

While square and cube roots are the most common, maths also deals with fourth roots, fifth roots, and so on.

Example Question 2

Find the cube root of 216.

Solution: ∛216 = 6 because 6 x 6 x 6 = 216

Order of Operations

To accurately solve mathematical expressions, one must adhere to a specific sequence. The acronym BIDMAS (sometimes known as BODMAS) is a handy reminder:

  • B: Brackets
  • I/D: Indices (Powers) and Division (from left to right)
  • M/A: Multiplication and Addition (from left to right)

Importance of BIDMAS

Following the BIDMAS rule ensures consistency in results. Without a set order, different mathematicians might interpret an equation in varied ways, leading to multiple answers for the same problem.

Example Question 3

Evaluate: 6 + 4 x 32 - 12 ÷ 3.

Solution:

  1. Powers: 32 = 9
  2. Multiplication: 4 x 9 = 36
  3. Division: 12 ÷ 3 = 4
  4. Addition and Subtraction: 6 + 36 - 4 = 38

Final answer: 38

Example Question 4

Evaluate: (7 + 5) x 32 ÷ 6.

Solution:

  1. Brackets: 7 + 5 = 12
  2. Powers: 32 = 9
  3. Multiplication: 12 x 9 = 108
  4. Division: 108 ÷ 6 = 18

Final answer: 18

FAQ

Powers, or exponents, have numerous real-world applications, especially in fields that deal with growth, decay, or scaling. For instance, in finance, compound interest calculations use exponents to determine the future value of investments. In biology, exponential growth describes population growth under ideal conditions. In physics, the inverse square law, which involves squared exponents, describes phenomena like gravity and electromagnetic forces. Understanding powers and their properties allows professionals in various fields to model, predict, and analyse situations accurately, making the concept not just a mathematical abstraction but a vital tool in understanding and navigating the world.

Zero and negative exponents play a fundamental role in understanding the properties of numbers and their behaviours. A number raised to the power of zero is always 1 (except when the base is undefined, like 00). This property highlights the idea of any number divided by itself (except zero) being 1. On the other hand, negative exponents indicate the reciprocal of the base raised to the corresponding positive exponent. For example, 2-3 is the same as 1/23 or 1/8. This concept reinforces the understanding of inverses in mathematics and showcases the symmetrical nature of mathematical operations.

While BIDMAS/BODMAS provides a general guideline for the order of operations, there are nuances to consider. For instance, when faced with operations of the same rank (like multiplication and division or addition and subtraction), one should perform them from left to right as they appear in the expression. Additionally, nested brackets should be resolved from the innermost set outward. It's also worth noting that some mathematical contexts or specific problems might have their own conventions or priorities, which could override the standard BIDMAS/BODMAS rule. As always, understanding the underlying principles and being attentive to context is key to accurate mathematical reasoning.

Fractional exponents and roots are closely related in mathematics. A fractional exponent, such as 1/2 or 1/3, represents a root. Specifically, if a number is raised to the power of 1/2, it's equivalent to taking the square root of that number. Similarly, raising a number to the power of 1/3 equates to taking its cube root. For instance, 9(1/2) is the same as the square root of 9, which is 3. This relationship provides a bridge between the concepts of powers and roots, allowing for more flexible mathematical expressions and simplifying complex calculations.

The order of operations, represented by the acronym BIDMAS/BODMAS, is crucial because it ensures consistency and clarity in mathematical calculations. Without a standardised order, the same mathematical expression could yield different results depending on the sequence in which operations are performed. This could lead to confusion, errors, and misinterpretations, especially in fields where precise calculations are essential, such as engineering, finance, and science. By adhering to BIDMAS/BODMAS, mathematicians and students can confidently approach problems, knowing that their methodology aligns with universally accepted standards, ensuring consistent and accurate results.

Practice Questions

Evaluate the following expression using the BIDMAS/BODMAS rule: 5^3 x 2^2 - 3^2 + 6 ÷ 2.

First, we'll evaluate the powers:53 = 12522 = 432 = 9

Next, we'll perform the multiplication:125 x 4 = 500

Then, the division:6 ÷ 2 = 3

Finally, we'll perform the addition and subtraction in sequence:500 - 9 + 3 = 494

Thus, the value of the expression is 494.

Find the value of x where the cube root of x is equal to the square root of 49.

First, we'll find the square root of 49:Square root of 49 = 7

Now, we'll set up the equation using the cube root:Cube root of x = 7

To solve for x, we'll cube both sides:x = 7 x 7 x 7x = 343

Thus, the value of x for which the cube root of x is equal to the square root of 49 is 343.

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