Box2D & Cocos2d-x finding future location of a body - cocos2d-iphone

Question

I'm in the process of making a mobile game and am having trouble predicting the future location of a body/sprite pair. The method I am using to do this is below.
1 --futureX is passed in as the cocos2d sprite's location, found using CCSprite.getPosition().x
2 -- I am using b2Body values for acceleration and velocity, so I must correct the futureX coordinate by dividing it by PTM_RATIO (defined elsewhere)
3 -- the function solves for the time it will take for a the b2Body to reach the futureX position (based off of its x-direction acceleration and velocity) and then uses that time to determine where the futureY position for the body should be. I multiply by PTM_RATIO at the end because the coordinate is meant to be used for creating another sprite.
4 -- when solving for time I have two cases: one with x acceleration != 0 and one for x acceleration == 0.
5 -- I am using the quadratic formula and kinematic equations to solve my equations.
Unfortunately, the sprite I'm creating is not where I expect it to be. It ends up in the correct x location, however, the Y location is always too large. Any idea why this could be? Please let me know what other information is helpful here, or if there is an easier way to solve this!
float Sprite::getFutureY(float futureX)
{
b2Vec2 vel = this->p_body->GetLinearVelocity();
b2Vec2 accel = p_world->GetGravity();
//we need to solve a quadratic equation:
// --> 0 = 1/2(accel.x)*(time^2) + vel.x(time) - deltaX
float a = accel.x/2;
float b = vel.x;
float c = this->p_body->GetPosition().x - futureX/PTM_RATIO;
float t1;
float t2;
//if Acceleration.x is not 0, solve quadratically
if(a != 0 ){
t1 = (-b + sqrt( b * b - 4 * a * c )) / (2 * a);
t2 = (-b - sqrt( b * b - 4 * a * c )) / (2 * a);
//otherwise, solve linearly
}else{
t2 = -1;
t1 = (c/b)*(-1);
}
//now that we know how long it takes to get to posX, we can tell the y location on the sprites path
float time;
if(t1 >= 0){
time = t1;
}else{
time = t2;
}
float posY = this->p_body->GetPosition().y;
float futureY = (posY + (vel.y)*time + (1/2)*accel.y*(time*time))*PTM_RATIO;
return futureY;
}

Answer 1

SOLVED:
The issue was in this line:
float futureY = (posY + (vel.y)*time + (1/2)*accel.y*(time*time))*PTM_RATIO;
I needed to explicitley cast the (1/2) as a float. I fixed it with this:
float futureY = (posY + (vel.y)*time + (float).5*accel.y*(time*time))*PTM_RATIO;
Note, otherwise, the term with acceleration was evaluated to zero.