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# Algebra watch

1. I know but I can't just give up on the question. I have to have a little bash at it
2. (Original post by fliss1992)
Here I have a question..

72
______ = 1

x^2 - 9 (...)

x² - 9 is the denominator of the term on the left side. That's why you have to multiply the equation by the denominator, so the denominator 'disappears' on the left side. You get:

.

-9 is is the subtrahend on the right side of the equation. You have to add the equation by 9, if -9 should dissapear on the right side. You get:

.

And now you take the root to get your result. It is x = 9.

As you can see, the result is right. Any questions?
3. (Original post by fliss1992)
I know but I can't just give up on the question. I have to have a little bash at it
I think MrM is suggesting that you need to get the basics in place before you tackle more advanced questions that depend on basic skills.

But just for information, when you have a problem like this where several operations take place, you have to reverse them in the correct order.

Your original problem is basically 72/something = 1. So what would you do to find "something"?
4. (Original post by davros)
I think MrM is suggesting that you need to get the basics in place before you tackle more advanced questions that depend on basic skills.

But just for information, when you have a problem like this where several operations take place, you have to reverse them in the correct order.

Your original problem is basically 72/something = 1. So what would you do to find "something"?
1 multiplied by 72?
5. (Original post by fliss1992)
1 multiplied by 72?
Not quite (although you do get the correct answer because 1 is a special number!)

You need to multiply both sides by "something" to get 72 = "something" x 1

And what is any number multiplied by 1?
6. (Original post by fliss1992)
72 multiplied by 9? 648

Or am I looking at the wrong calculation?
Out of curiosity, if someone said "6 divided by something is 2, what is the something?", would you be able to work it out?
7. the 'something' would be 3
8. (Original post by Mr M)
Thanks for the explanation. I feel much better informed now.
And thanks for the sarcastic remark- a lot easier than making meaningful conversation, i'd imagine.

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