Chapter-9 - Problem 9.3-1.1x1 10x2=120-2x1 17.4x2=174(a Solve it graphically To solve graphically we express x2 in terms of x1 for both equations

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Problem 9.3 -1.1x 1 +10x 2 =120 -2x 1 +17.4x 2 =174 (a) Solve it graphically. To solve graphically we express x2 in terms of x1 for both equations, plot the two lines and see where they intersect. x2=@(x1) (120+1.1*x1)/10 x2 = @(x1) (120+1.1*x1)/10 And for the second equation >> x2a=@(x1) (174+2*x1)/17.4 x2a = @(x1) (174+2*x1)/17.4 In order to look for a graphical solution, we need to select a range to plot the functions. If we solved the problem only for x1 we would get values of the order of 100, and if we solved only for x2 we would get values of the order of 10. So we could try (0,200) for x1 >> fplot (x2,[0,200]); hold on >> fplot (x2a,[0,200])
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Obviously the solution is further away, so we try again. >> fplot (x2,[200,500]); hold on >> fplot (x2a,[200,500]) 0 20 40 60 80 100 120 140 160 180 200 10 15 20 25 30 35
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Now we are the right range but it is too broad to tell intersection. So we zoom >> fplot (x2,[350,450]); hold on >> fplot (x2a,[350,450]) 200 250 300 350 400 450 500 30 35 40 45 50 55 60 65 70
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We can continue to zoom. The exact solution is >> A=[-1.1 10;-2 17.4] A = -1.1000 10.0000 -2.0000 17.4000 >> b=[120;174]; sol=A\b sol = 404.6512 56.5116.
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This note was uploaded on 03/27/2012 for the course EGM 3344 taught by Professor Raphaelhaftka during the Spring '09 term at University of Florida.

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Chapter-9 - Problem 9.3-1.1x1 10x2=120-2x1 17.4x2=174(a Solve it graphically To solve graphically we express x2 in terms of x1 for both equations

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