# Rules of Indices

^{m};

**a**is called the base and

**m**is the power. The power is also often referred to as the “index” or “exponent”.

Indices rules only apply when the base is the same for all terms. This is very important to remember.

Below is the indices rules that you should familiar with. Notice that the a is constant within each rule.
## First indices rule

In the multiplication rule we only need to add the powers.

Since the base is the same in both terms the multiplication is just a continuation. To observe this expand the expression;
The total number of as in the expansion is equal to the sum of powers in the question. This proves that; a

The example below shows where this rule applies.
^{n}x a^{m}= a^{n+m}
Example: Workout 2

^{5}x 2^{6}
Answer

2

^{5}× 2^{6}= 2^{5+6}= 2^{11}
ExplanationWe must use the indices multiplication rule, we simply just add the powers.

It’s is important to leave the answer in indices. 2

^{11}is much easier to remember than 2048.Leaving the answer in indices form is particularly helpful when working with very large indices. 9

We can expand the expression to see exactly what is going on.
^{8}is much easier to remember than 43046721.2

^{5}= 2 × 2 × 2 × 2 × 2…and…

2

^{6}= 2 × 2 × 2 × 2 × 2 × 2We can continue to multiply the two products together.

2

^{5}× 2^{6}= 2 × 2 × 2 × 2 × 2 × 2 × 2 × 2 × 2 × 2 × 2 = 2^{11}…therefore…

2

^{5}× 2^{6}= 2^{11}## Second indices rule

This rule of indices is known as the power of a power. A number with a power can be raised to a power eg; a^{5}to the power 2. This expression simply means; …we know that the first rule tells us that we should add the indices power together for multiplication; But note also that 5×2 is equal to 10. This suggests that if we have a

^{m}raised to the power n we simply multiply the powers together to get the result a

^{mxn}or simply a

^{mn}, this is proof for the second rule. Below are some examples of how to use this rule.

Example: Work out (4

^{5})^{2}:
Answer
The power of two means that we want to have 4

^{5}multiplied by itself 2 times. In this case we simply just multiply the powers together.This example proves the general rule of indices that (a

^{n})^{m}= a^{nm}The answer for the above question is actually a very large number of

**1048576**so you can see why it is important that you leave your answers in indices form.## Third indices rule

This rule states that for the division of two powered numbers, the result is equal the base to the power of the difference between the two powers as shown in the following example.
Example: Work out 4

^{8}÷ 4^{2}
Answer: Expand the expression first to observe what is going on.
We can now use cancelling to simplify the expressions.
There has been two cancellations which proves that we only need to find the difference between the two powers as shown below.

Remember to leave your answers in indices, rather than the actual value. This is useful when carrying out much large/complex calculations.
## Fourth Indices Rule

The fourth rule: a

^{0}= 1### Proof

We know that 2/2 = 1 the same is true to any number divide by it self;*4/4 = 1, 7/7 = 1, 40/40 = 1*

a

Notice here that we can use the indices rule of subtraction (third rule) which states that;
^{m}/a^{n}= 1a

We can replace m and n by the same number such that the number in the numerator is equal to the number in the denominator. To make sure that when we divide (equal numbers) we get 1.
if we replace m and n with a single number;
^{m}÷ a^{n}= a^{m-n}(a

^{m})/(a^{m})=a^{(m-m)}= a^{(0)}= 1 ≡ (a^{m})/(a^{m})…or…

(a

^{n})/(a^{n})=a^{(n-n)}= a^{(0)}= 1 ≡ (a^{n})/(a^{n})Dividing a number by itself = 1

We can use actual numbers;
(a

^{1})/(a^{1})=a^{(1-1)}= a^{(0)}= 1 ≡ (a^{1})/(a^{1})(a

^{2})/(a^{2})=a^{(2-2)}= a^{(0)}= 1 ≡ (a^{2})/(a^{2})(a

^{20})/(a^{20})=a^{(20-20)}= a^{(0)}= 1 ≡ (a^{20})/(a^{20})(a

^{100})/(a^{100})=a^{(100-100)}= a^{(0)}= 1 ≡ (a^{100})/(a^{100})## Fifth Indices Rule

The following indices rule deal with negative and fractional powers.The fifth rule: a

^{-1}= 1/a and a^{-m}= 1/a^{m}Be careful here 2

Look at the pattern below;
By looking at the worked out indices above do you note a pattern?
A negative power on any number creates a reciprocal of that number. You can learn more about reciprocals here.
If you’re to work it out on your calculator you might get one of these variations;
The general rule for negative powers is;
^{-4}is not the same as 2^{4}and it should not be related in anyway.
Example: Work out (2/3)

^{-5};
Answer: We have to work out;
The reciprocal of;
That must mean that;
Next we simply power the denominator and numerator separately as shown below;

## Sixth Indices Rule

The indices rule shown above is known as a fractional indices rule. This is the simpler version but is not different from the one shown below. You must know that anything to the power 1 is itself. So the expression shown below must be true; The expression above implies that a^{½}is the √a. That proves the above rule that; It also proves that; …because… This forms the general indices rule for fractional powers;

Now we shall look at an expansion to this rule. The indices rule explained above is derived from the following rule in fact. We have not powered the final answer with 1 because x to the power of 1 is equal to x. This is just the harder fractional indices rule.

Example: Workout 27

You can see how this rule and the above are quite similar. We can split up any fractional power into a root followed by a power as shown below;
^{2/3}.
Answer:
Here we could use the brackets rule by first breaking the power into parts.
Thus we could write;
Now we could use the rule for fractional powers.

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Thanks for this, very helpful stuff

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HELP!!!! I need to know what rule five is for a test tomorrow!! It says in my book:

2(in powers) -3=1 over 2, to the power 3= 1 over 8??? can

someone explain please?????

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Sorry, I could not get to your comment in time. I will be updating this entry with more content very soon.

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it is kind of unclear of how the rules are divided and explained because i think they are more rules. so that was kind of unclear.

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I will be updating this entry to make certain sections clearer very soon.

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what is A raise to the power x or A raise to the power 2x .

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A very helpful explanantion – thank you.

In the last line of rule four (just over the rule five title) am I right in thinking that the first fraction has been (inadventently) turn over again?

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my mind is fully clear after seeing this. thankyou.

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Thanks for dis!!!!

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Really helpful. Cheers

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Hey I need help.

How do you solve 3 to the power of 100 times 4 to the power of 100?

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Hi is that

\[ 3^{100} × 4^{100} \]

Remember you cannot apply any rule here since the bases for both numbers is different.

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You can simplify it to (3×4)^100, i.e 12^100

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thanks this really helps when trying to revise

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Thanks…How does the rule apply when adding or subtracting the same bases but powers eg. X^a + X^b

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Hello Lamin,

As you have seen above you can’t apply any of the rules if it is addition.

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Because its brackets basic multiplication and division they ARRRREEE the 3 rules though.

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awesome

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quite good

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how to solve

10^n – 4^n / 5^n – 2^n

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THANK YOU

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thx

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this is very help full web but i cant find the quation’s like

a1 over 2 x a-3 over 4

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this is very help full web but i cant find the quation’s like this one

a1 over 2 x a-3 over 4

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Hi most of your notes i find easy to understand but below my teacher (i’m an adult learner)he as given us stuff to reduce to a single index i have brackets within in brackets and fractions inside that and powers i’m confused have you a page i can look at please?

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Hello Thomas,

Can you type some examples of the questions that your teacher wants you to work out. Brackets means multiply so you might have to expand the expressions first. Are they similar to this:

\[(x^2y^3) ÷ (x^2y^4) \]

\[ (4^2(4×4×4)) × ((4×4×4)4^5) \]

Remember indices rules only apply when the base for all the terms is the same to be able to reduce it to a single indexed number.

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Hi, I am having difficulty working out this question. Can anybody help ?

5×2/3=x-1/3

The answer is 1/5 but I am having trouble getting to that answer.

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Probably not a problem still but thought i would answer anyway. times both sides by three cancels the division on both sides, adding 1 to both sides cancels the -1 on the right side and then you have 11= x

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i like mathematics

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