xylia Posted April 10, 2014 Share Posted April 10, 2014 I'm having some difficulty solving this problem, we have x on the graph and its unknown , the gradient is of a straight line is 2.3 x10^4 the interception on the y axis is 5.8 x10^4 m we know y is 6.2x10^5 m i need to find x so i tried rearranging the equation y=mx+c to get x=y/m-c but i get a rely high number so I'm guessing its not correct please help me Link to comment Share on other sites More sharing options...
Lizzie L Posted April 10, 2014 Share Posted April 10, 2014 I'm having some difficulty solving this problem, we have x on the graph and its unknown , the gradient is of a straight line is 2.3 x10^4 the interception on the y axis is 5.8 x10^4 m we know y is 6.2x10^5 m i need to find x so i tried rearranging the equation y=mx+c to get x=y/m-c but i get a rely high number so I'm guessing its not correct please help me Well, those are big numbers! Can you write down the equation for the line? Is it y=2.3 x10^4x + 6.2x10^5? If so, you just need to think again about your rearrangement Link to comment Share on other sites More sharing options...
Tim the plumber Posted April 10, 2014 Share Posted April 10, 2014 25 years since I did any of this but 24.43 is my answer. Link to comment Share on other sites More sharing options...
xylia Posted April 10, 2014 Author Share Posted April 10, 2014 right because y=mx Link to comment Share on other sites More sharing options...
Lizzie L Posted April 10, 2014 Share Posted April 10, 2014 (edited) Well, y=mx+c right? That's the equation for your line. You know that y is 6.2x10^5 You know that the intercept, c is 5.8 x10^4 And you know that m (presumably) is 2.3 x10^4 So, as you say, you just have to rearrange: y = mc + c. Subtract c from both sides: y - c = mx. Now divide both sides by m, and then substitute your known values Edited April 10, 2014 by Lizzie L Link to comment Share on other sites More sharing options...
xylia Posted April 10, 2014 Author Share Posted April 10, 2014 yes right but isn't that what i did? Link to comment Share on other sites More sharing options...
Lizzie L Posted April 10, 2014 Share Posted April 10, 2014 yes right but isn't that what i did? Well, y=mx+c doesn't turn into x=y/m-c ! I'm trying to get you to do the last line yourself! First subtract c from both sides: y- c = mx + c - c. So that gets you to y-c = mx Now divide both sides by m. That gets you to (y-c)/m = mx/m, Right? Which gets you to....get it? Link to comment Share on other sites More sharing options...
xylia Posted April 10, 2014 Author Share Posted April 10, 2014 (y-c)/m=x Link to comment Share on other sites More sharing options...
Lizzie L Posted April 10, 2014 Share Posted April 10, 2014 (edited) Yup. Now substitute your values for y, m and c, and you are done Edited April 10, 2014 by Lizzie L Link to comment Share on other sites More sharing options...
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