find x given y

%W=3t^2+6t
%W=3t(t+2)
%(-(b)+sqrt(b^2-(4*a*c))/2*a)
%(-(b)-sqrt(b^2-(4*a*c))/2*a)
syms x
W=3*x.^2+6*x;
t1a=solve(3*x.^2+6*x == 3);
t2a=solve(3*x.^2+6*x == 9);
t3a=solve(3*x.^2+6*x == 45);

this is what i have right now but i only want the possitive x value

Answer 1

[Walter Roberson]

syms x positive
W=3*x.^2+6*x;
t1a=solve(W == 3)

t1a = 

t2a=solve(W == 9)

t2a = 

1

t3a=solve(W == 45)

t3a = 

3