Not the right answer

float comppoly(x)
{
  float y1, y2;
  float a1=0.1, b1=0.3, a2=2.1, b2=5.3, c=0.22;

  y1 = (a1 * x)   +  b1;
  y2 = (a1 * x^2) + (b2 * x) + c;

  return(y2 > y1);
}

or (more math):

float comppoly(x)
{
  float y1, y2;
  float a1=0.1, b1=0.3, a2=2.1, b2=5.3, c=0.22;

  y1 =              (a1 * x) + b1;
  y2 = (a1 * x^2) + (b2 * x) + c;

  return(y2 > y1);
}

or (simple):
float comppoly(x)
{
  float y1, y2;
  float a1=0.1, b1=0.3, a2=2.1, b2=5.3, c=0.22;

  y1 = a1 * x   + b1;
  y2 = a1 * x^2 + b2 * x + c;

  return(y2 > y1);
}

I made it readable and corrected a minor error :-)
Breakets are not only for compiling, they also increase the readabillity.

.
BR,
/th.

float comppoly(x)
{
  float y1, y2;
  float a1=0.1, b1=0.3, a2=2.1, b2=5.3, c=0.22;

  y1 = (a1 * x)   +  b1;
  y2 = (a1 * x^2) + (b2 * x) + c;

  return(y2 > y1);
}

or (more math):

float comppoly(x)
{
  float y1, y2;
  float a1=0.1, b1=0.3, a2=2.1, b2=5.3, c=0.22;

  y1 =              (a1 * x) + b1;
  y2 = (a1 * x^2) + (b2 * x) + c;

  return(y2 > y1);
}

or (simple):
float comppoly(x)
{
  float y1, y2;
  float a1=0.1, b1=0.3, a2=2.1, b2=5.3, c=0.22;

  y1 = a1 * x   + b1;
  y2 = a1 * x^2 + b2 * x + c;

  return(y2 > y1);
}

I made it readable and corrected a minor error :-)
Breakets are not only for compiling, they also increase the readabillity.

.
BR,
/th.

It wouldn't hurt giving the input parameter x a data type too.

LOL, didn't see that (just looked at the code) :-)

My ChrystalBall assumes:

float comppoly(float x)
{
  float y1, y2;
  float a1=0.1, b1=0.3, a2=2.1, b2=5.3, c=0.22;

  y1 = (a1 * x)   +  b1;
  y2 = (a1 * x^2) + (b2 * x) + c;

  return(y2 > y1);
}

So, I guess that the compiler warns, and assumes int. That of course gives the wrong answer if fed with float ...

.
BR,
/th.

float comppoly(float x)
{
  float y1, y2;
  float a1=0.1, b1=0.3, a2=2.1, b2=5.3, c=0.22;

  y1 = (a1 * x)   +  b1;
  y2 = (a1 * x^2) + (b2 * x) + c;

  return(y2 > y1);
}

Hah. Now it won't even compile (on a sane compiler). Not exactly a big improvement, is it?

:->

x^2 is a bit problematic when x is a float.

But then again - it is a bit problematic when x is an int too...