Algebra: Chapter 8-2, p 362
The Substitution Method
You can solve a system of equations by substituting for a variable. If there are 2 equations,
`x + y = 6` and
`x = y + 2`
then using the information from the second equation, we can plug in for `x`, the values `y +2` in the first equation. It then looks like,
`(y +2) + y = 6` or combining like terms
`2y + 2 = 6` or subtracting 2 from both sides,
`2y + 2 − 2 = 6 − 2` or
`2y = 4` or
`y = 2`.
Once we have `y`, go back to one of the two equations and solve for `x`. If `y = 2`, then `x = 4`!
Math 8, Chapter 5-9, p259
An arithmetic sequence is a sequence in which the difference between any 2 consecutive terms is the same. Geometric sequences have differences that are multipliers or dividers. Today’s lesson is just about arithmetic sequences however. Arithemtic sequences can be additive or subtractive. The difference is referred to as the the COMMON DIFFERENCE.
Here is a link from purplemath with examples.