solve by substitution method

4x+5y=-15
x=3-8y

[Matt Tearle]

Do you have a MATLAB question?

Answer 1

[Matt Fig]

Do you have a question? One related to MATLAB?

[Matt Tearle]

attack of the Matt Police!

[Matt Fig]

HaHa, I didn't even see your first comment till now!

Answer 2

[Walter Roberson]

syms x y
yexpr = solve(4*x+5*y+15*x,y);
xval = solve(subs(3-8*y+15*x,yexpr),x);
yval = solve(subs(4*x + 5*y + 15*x, x, xval),y);

(There is at least one shorter method.)

Answer 3

[omer ozdemir]

how can be solved this problem?

suppose that a polynominal can be expressed by

 f(x)= x^5+3*x^4+4*x^3+2*x^2+3*x+6

If one wants to substitute x by s-1/s+1, the function f(x) can be changed into a function of s.

thanks.

[Walter Roberson]

You can use subs() and simplify() from the Symbolic toolbox.

Note that f(s) will not be a polynomial.

[omer ozdemir]

thanks.