Raider5678 Posted November 8, 2016 Share Posted November 8, 2016 Hey, I have a question about math. If you take : - 8 = 3/19 n (imagine the 3/19 as a fraction.) you need to find N. To do this you would flip the 3/19 to get 19/3 and put it of the other side of the equation. Getting: 19/3 * -8/1 = n Getting in the end the answer: -152/3 = n How does this give the answer? Link to comment Share on other sites More sharing options...

Strange Posted November 8, 2016 Share Posted November 8, 2016 The moving-a-fraction-to-the-other-side-and-flipping-it is shorthand for the following steps (based on the fact that if you multiply both sides by the same number then the equality is still true): 1. multiply both sides of the equation by 19 - this cancels with the /19 on the RHS 2. divide both sides by 3 - this cancels with the 3 on the on the RHS You are left with the LHS multiple by 19/3 and n on the RHS. 1 Link to comment Share on other sites More sharing options...

DrKrettin Posted November 8, 2016 Share Posted November 8, 2016 (edited) Look: the principle is that when you have A = B then you can perform the same operation on both sides and the statement is still true. By that I mean you can multiply both sides by 19/3 So -8.19/3 = 3/19 n . 19/3 I did that because that makes the numbers on the RHS cancel out, giving -152/3 = n. Easy Edit - cross-posting with Strange, as usual Edited November 8, 2016 by DrKrettin Link to comment Share on other sites More sharing options...

Strange Posted November 8, 2016 Share Posted November 8, 2016 Edit - cross-posting with Strange, as usual Link to comment Share on other sites More sharing options...

Raider5678 Posted November 8, 2016 Author Share Posted November 8, 2016 The moving-a-fraction-to-the-other-side-and-flipping-it is shorthand for the following steps (based on the fact that if you multiply both sides by the same number then the equality is still true): 1. multiply both sides of the equation by 19 - this cancels with the /19 on the RHS 2. divide both sides by 3 - this cancels with the 3 on the on the RHS You are left with the LHS multiple by 19/3 and n on the RHS. Thanks. Link to comment Share on other sites More sharing options...

Sriman Dutta Posted November 8, 2016 Share Posted November 8, 2016 Hey, I have a question about math. If you take : - 8 = 3/19 n (imagine the 3/19 as a fraction.) you need to find N. To do this you would flip the 3/19 to get 19/3 and put it of the other side of the equation. Getting: 19/3 * -8/1 = n Getting in the end the answer: -152/3 = n How does this give the answer? That's a property of linear equations. Link to comment Share on other sites More sharing options...

Raider5678 Posted November 8, 2016 Author Share Posted November 8, 2016 That's a property of linear equations. This isn't a linear equation. You can't even apply it to a graph. Link to comment Share on other sites More sharing options...

Sriman Dutta Posted November 8, 2016 Share Posted November 8, 2016 This isn't a linear equation. You can't even apply it to a graph. True....It cannot be plotted in a graph. Link to comment Share on other sites More sharing options...

Country Boy Posted November 8, 2016 Share Posted November 8, 2016 It is a linear equation, of the form "An= B" with A= 3/19 and B= -8. It is not a linear function so cannot be graphed- though you could think of it a point on the graph y= (3/19)x at y= -8. Link to comment Share on other sites More sharing options...

Raider5678 Posted November 8, 2016 Author Share Posted November 8, 2016 It is a linear equation, of the form "An= B" with A= 3/19 and B= -8. It is not a linear function so cannot be graphed- though you could think of it a point on the graph y= (3/19)x at y= -8. Didn't think it worked like that. Link to comment Share on other sites More sharing options...

deesuwalka Posted November 9, 2016 Share Posted November 9, 2016 (edited) Here is the solution- [latex] -8=\dfrac{3}{19}n [/latex] Now, multiply both sides by [latex] 19 [/latex] [latex] -8\times 19=\not19 \times\dfrac{3}{\not19}n [/latex] [latex] -152=3n [/latex] Now, divide both sides by [latex] 3 [/latex] [latex] \dfrac{-152}{3}=\dfrac{3n}{3} [/latex] [latex] \dfrac{-152}{3}=n [/latex] Edited November 9, 2016 by deesuwalka Link to comment Share on other sites More sharing options...

Country Boy Posted November 9, 2016 Share Posted November 9, 2016 Back in my dark past, when I was teaching basic algebra, I always discouraged students from saying "move a number from one side of the equation to another". With something like "ax= b" many students would come up with x= - b/a. Then when I pointed out that the answer should be b/a, they would complain "but I thought that when you moved a number from one side to the other you had to change the sign!". Instead I tried to teach them to think in terms of "reversing" whatever is done to x. In ax= b, x is multiplied by a. To reverse that do the opposite: divide by 3. And, of course, whatever you do to one side you must do to the other: ax/a= x= b/a. If the equation were x+ a= b, then, since a is added to x, we do the opposite: subtract a: x= a- b. Link to comment Share on other sites More sharing options...

Raider5678 Posted November 9, 2016 Author Share Posted November 9, 2016 Back in my dark past, when I was teaching basic algebra, I always discouraged students from saying "move a number from one side of the equation to another". With something like "ax= b" many students would come up with x= - b/a. Then when I pointed out that the answer should be b/a, they would complain "but I thought that when you moved a number from one side to the other you had to change the sign!". That would be from the students not actually thinking through the process and simply trying to get the answer. They must also understand how it works if they are to understand how to get the answer. Perhaps it gets them through, but it won't be useful in the long run. Link to comment Share on other sites More sharing options...

## Recommended Posts

## Create an account or sign in to comment

You need to be a member in order to leave a comment

## Create an account

Sign up for a new account in our community. It's easy!

Register a new account## Sign in

Already have an account? Sign in here.

Sign In Now