To find the sum<span> of a </span>positive<span> and a </span>negative integer<span>, take the </span>absolute value<span> of each </span>integer<span> and then subtract these </span>values<span>. The result takes the sign of the </span>integer<span> with the larger </span>absolute value<span>. The </span>sum<span> of any </span>integer<span> and its opposite is equal to zero.</span>
The absolute value is always equal to the module (or positive value) of a number:
IxI = x if x>0
IxI = -x if x < 0
suppose you have an addition of two numbers of the same sign:
If both numbers are positive, the sum will be positive, if both numbers are negative, the sum will be negative, but now let's see the case where the sign of the numbers is different:
Here, you can apply the absolute value to both numbers, and the sign of the addition will be the same sign of the number associated with the biggest absolute value.
Set up for both orders of integration for the integral below where R is the arc of a circle radius 2 in the first quadrant. Show that both orders produce the same result by integrating each of them.
