why i get undefined reference when I use math functions?

Is anyone know why I get this type of error, and how to solve it? Thanks a lot!!! I tried lots of math functions, but none of them works…

The output i get:

qcc tryfirst.c -o try

/tmp/AAA567656_cc.o: In function main': /tmp/AAA567656_cc.o(.text+0x2b): undefined reference to pow’
cc: /usr/ntox86/bin/ld error 1

The code I have:
#include <math.h>
#include <stdio.h>
#include <stdlib.h>

int main( void )
double value;

value = pow( 2.3, 2.0 );   


you need to link with the math library:

qcc tryfirst.c -o try -lm