# Algebraic Fractions: Addition and Subtraction

So what do I have to multiply to 11 to make 66, 6 isn’t it? So we have to multiply this denominator by 6.
But guys, remember you can’t just multiply the denominator by six if you’re doing something to the bottom, you must do the same thing to the numerator to the top.
So I’m going to multiply six to bottom and top for this fraction. Now, what do I have to multiply to six to get sixty-six? This time we have to multiply 11, don’t we?
I’m going to multiply 11 to 6. But again you have to do the same thing to the top.
This is what I’m going to do multiply 6 to top and bottom for this fraction and multiply 11 to both top and bottom for this fraction. Okay?
And then just simplify so what’s 6 times 8x 48 and 6 times 11 is 66 same for this one and 11 times 5 is 55. So 55x. Okay? So can you see that now we have the same denominator?
Now keep that denominator and you merge the numerators. So you do 48x minus 55x. What is that? All of you should be able to do this. It’s negative 7.
So negative 7x sorry so negative 7x over the same denominator 66 is your answer. So you leave the denominator as 66, Okay? Let’s do the same thing.
What is common what’s the common multiple the lowest common multiple of 3 and 5? It should be 15, isn’t it? So I need to multiply 3 by 5 and 5 by 3 to get that same 15.
Make sure when you’re multiplying by five you do it to the top as well as the bottom and when you’re multiplying by three you do it to both top and bottom like that.
Here we have 5x over 15 and here we have 6x over 15. So we have the same denominator. All you need to do is merge the numerator. So 5x plus 6x is 11x, so it’s 11x over 15, Okay?
So you keep the denominator the same all the time all right? Easy peasy.
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