Question 1088147
factor into (2x-1)(x+3)=0
x=1/2,-3
check 
f(1/2)=1/2+2.5-3=0
f(-3)=18-15-3=0
{{{graph(300,300,-5,5,-10,10,2x^2+5x-3)}}}
Unless the problem was copied incorrectly, Mathlab is wrong if they say those aren't the roots.  Both of them make y=0 (an x-intercept) and graphically work.