Hello,

There is already mentioned few times about solving equations with solve() and roots().
The solve() function has a searching algorithm trying to find all the real roots in the given range, and it can fail like most of the numerical procedures. It is advisable to use 4 arguments solve(). The default range is set by default to [-20,20] - Tools|Options|Calculation|Roots range - where it is not suitable in some cases (like in yours)

In your case:
a←1b←263.84c←-61463
f(x)←a*x^2+b*x+c
solve(f(x),x,-450,150)=#@#
solve() will probabely fail. Therefore, you can try to find the roots one by one:
solve(f(x),x,-500,-300)=-412.7507
solve(f(x),x,100,200)=148.9107
or using roots()
roots(f(_x),_x,-400)=-412.7507
roots(f(_x),_x,150)=148.9107

Regards,
Radovan

Edited by user 18 June 2011 17:47:58(UTC)  | Reason: Not specified