Lesson video

Hi, I'm Miss Davies.

In this lesson we're going to be subtracting algebraic fractions that have integer denominators.

When subtracting algebraic fractions, you treat them in the same way as you do ordinary numerical fractions.

With this question, eight y over seven subtract three y over seven, we don't need to use equivalent fractions to adjust our denominators, as they are already the same.

So this fraction simplifies to five y over seven.

The denominator always stays the same.

With our next question we have got t terms and numerical terms in our numerator.

But again, our denominators are the same.

Seven t subtract four t is three t and four subtract three is one.

This simplifies to three t add one all over four.

In our next example, it is a little bit trickier, as the negative eight in our second fraction.

So we are going to do four p subtract three p.

This is equivalent to one p, which we'll write as p.

We've then got positive five subtract negative eight.

This is equivalent to five add eight, so it gives us 13.

This simplifies to p add 13 all over three.

Here are some questions for you to try.

Pause the video to complete your task and resume once you're finished.

Here are the answers.

Make sure that you have fully simplified your final answers.

With this next set of questions, we're going to have to use equivalent fractions to adjust our denominators.

Seven is a factor of 21, so 21 is our lowest common denominator.

y over seven is equivalent to three y over 21.

This then simplifies to y over 21.

With our next example, 24 is a multiple of four.

So we're going to multiply all terms in our first fraction by six.

This gives us 18 t add 24 over 24.

We can then simplify this to give us 14 t add 21 over 24.

In our final example, nine is a multiple of three.

So nine is our lowest common denominator.

This is equivalent to four p add five all over nine subtract nine p subtract 24 all over nine.

Again, we've got five subtract negative 24.

This is equivalent to five add 24.

This expression simplifies to negative five p add 29 all over nine.

We could also write this as 29 subtract five p all over nine.

Here are some questions for you to try.

Pause the video to complete your task and resume once you're finished.

Here are the answers.

Eva has forgotten that subtracting negative 28 is equivalent to adding 28.

The correct answer was six y add 29 over eight.

Here are some questions for you to try.

Pause the video to complete your task and resume once you're finished.

Here are the answers.

Make sure that you have fully simplified your final answer.

For part d, don't forget that 10 subtract negative five is 15.

Here is a question for you to try.

Pause the video to complete your task and resume once you're finished.

Here is the answer.

To work out this problem, you needed to work out 10 a plus two over 12 subtract a plus five over three.

This gives six a subtract 18 over 12.

Well done if you simplified this to a subtract three over two.

That's all for this lesson.

Thanks for watching.