Pre-Algebra: Chapter 2-2
Coordinate systems are today’s agenda. First, we plot the x and then the y axes values. Where the 2 axes intersect is at (0,0) or the ORIGIN.
The x axis goes left to right or right to left and the y axis goes up and down or down and up. These we write as (x,y) and we call these ORDERED PAIRS.
The x axis has positive values to the right of the origin.
The x axis has negative values to the left of the origin.
The y axis has positive values above the origin
The y axis has negative values below the origin.
There are 4 quadrants on a graph in relation to the origin, the upper right is quadrant I, the upper left is quadrant II, the lower left is quadrant III and the lower right is quadrant IV. We write these in Roman numerals. Ordered pairs on either the x or y axes ARE NOT IN A QUADRANT.
Algebra: Chapter 2-4
Today, we are working on subtraction of rationale numbers. Remember, just do the inverse of subtraction and ADD the inverse (or opposite) of the number to the other number.
Examples:
A) -5 – 7 is really -5 + (-7) remembering that the + sign is invisible. So this becomes just -5 + (-7) and remembering the adding rule of 2 negatives, the answer becomes -12.
B) -4 – (-5) is really -4 + 5 because 2 negative are a positive (bing-bing! from Ms. Phillips) and the answer is +5 – 4 and the final answer is +1