How I can solve this integration numericaly in C++?

integration{x * exp(-itx) / [ax^3 + bx^2 + c] } ;

(Interval for x is from -inf .. inf) & (t ,a ,b ,c are constants);

Er, you seem to have posted this four times??

There's no "built-in" way to do this in C++, you will have to write a program to do it. Start by looking up "numerical integration" on the internet and trying to make a program to do the things that you find out. When you have some code that you've written, then you might be able to get a bit more help.