Plot two functions in one diagramm with different y-axis limits

Does someone know how i could solve the following Problem:

%x_1,...,x_7 are real valued Variables (which are generated before)
g = 0.5*x_1*(x_2*f_1-x_3*f_2)^2+x_4*f_1+x_5*f_2+x_6-x_7; 
funct = solve(g,f_2,'Real',true,'ReturnConditions',true);

y_lim = [10,15];
syms f_1
assume(funct.conditions);

funct.f_2(isAlways(funct.f_2 < y_lim(1),Unknown="falseWithWarning")) = NaN;
funct.f_2(isAlways(funct.f_2 > y_lim(2),Unknown="falseWithWarning")) = NaN;

fplot(funct.f_2, [7,50] ,'Color', 'b');

So i want to plot the quadratic function "funct" in the y-Intervall [10,15] and x-Intervall [7,50] but i get the (4) Warnings:

Warning: Unable to prove '(423*f_1)/77 - (576460752303423488000000*(7353528183219767092002251709184784741/324518553658426726783156020576256000000 -
(907661965900503303521461870041895139*f_1)/16615349947311448411297588253504307200000)^(1/2))/18611613717480648557 -
86464670358732992000000/18611613717480648557 < 10'. 
> In symengine
In sym/isAlways (line 41)

So the function gets plottet and the x-Interval is respected, but not the y-Interval. If i set Unknown="true" my function is not plotted at all. Do you know how i could plot the function "funct" correctly (in both intervals)? Thanks