using syms x to create an equation Y(x), then letting x be a vector to plot, x vs Y

using syms x I have created an equation

Y = (x/20 - 2)*(x/40 - 1) - (x/20 - 1)^2 + x^2/800

I would now like to set x = to a vector say [0:0.1:40] and would like plot(x,Y)

how can i implement this because when i try plot(x,Y) i get an error of

EDU>> plot(x,Y) ??? Error using ==> plot Conversion to double from sym is not possible.

Answer 1

[Walter Roberson]

xvals = 0:0.1:40;
plot(xvals, double(subs(Y, x, xvals)))

[Nicholas]

i keep getting a straight line

[Nicholas]

i tried it with other functions and it seems to work i dont know why my equation is linear but thank you

[Walter Roberson]

That equation does evaluate to 1. Expand the first multiplication, expand the squared term, add the two together, then note that the x^2 term cancels with the remaining term in Y, leaving just 1.