Evaluating Expressions

[joeyke]

How do I go about writing a program that finds and prints the values of result for all even values of y from 2 to 16, using the following formula:
result= (y-1) + (y+4)3
y -
1
y

* the 3 is power to 3
*the denominator means y minus 1 over y, just couldn't get it to stay on the same line.
I just don't know where to start. please help!

[Banfa]

                        3
           (y-1) + (y+4)
result=    --------------
             (y-1) / y

You start by working out how to write a loop that will iterate through the even integers 2 - 16. You look in math.h or a reference book for functions that are going to be useful (pow I suggest) and you code your equation probably not on a single line of code.

Remember that for all y > 0 (y-1) / y in integer arithmetic is 0
also remember that divide by (y-1) / y is the same as multiply by y / (y-1)
also remember that for all y > 2 y / (y-1) in integer arithmetic is 1

and finally remember that for multiply by y / (y-1) it is sometimes better to multiply by y then divide by (y-1) rather than calculating y / (y-1)

[joeyke]

this is what i did so far but i know i'm totally off

#include <cmath>
#include <iostream>
using namespace std;
int main()
{

double y;

cout<<" Enter an value for y: ";
cin>>y;

double check;
check=(y>0)+((y-1) / y))+((y > 2 y / (y-1));
cout<<" y= ";
cin>>y;

if (check>0)
{
y=(y........... .);


system ("pause");
return 0;
//i left the y=(y.......); blank because i have no idea what to do there!

[whodgson]

Go back and reread Banfa`s post
You need a for loop to iterate through the even numbers b/n 2 and 16. Also to use the pow() function from the <cmath>header .
double a = double pow(double(y+4) ,double 3) or a=pow(y+4,3)
Of course y+4 cubed is nothing more than (y+4)*(y+4)*(y+ 4).
I would suggest you leave your checks out until later and use if statements to control y values like if(y=0)y=1;