This is great practice for generating the Y= using the TI-84 linear regression feature
We must create 2 lists with Stats, Edit
Put the x values into L1 and the y values into L2
If there is already data in a list, press the up arrow until you get to L1 (or L2) and press clear, enter
Then Stats, right arrow, Calc, 4 enter for Linear regression and there you have it!!!
The equation of the line…match it up with one of the answers :)
One of the few things to memorize for the Regents is the formula for compound interest:
A = P(1 + r)^t
A is the account balance or amount
P is the principal or initial amount = 3000
r is the rate 4.2 % we need to convert this to a decimal
t is time
so the equation is:
A = 3000 (1 + .042)^t or it can be written as: A = 3000 (1.042)^t
That’s it — just writing this equation is 2 points!!
Please visit this blog post for a related multiple choice item from Jan 2016:
Get the Math and Get the Points Jan 2016 CC Alg I Regents #8
Students greatly benefit from knowing how the long answers on their tests will be scored.
44% of the exam is now non-multiple choice (38/86 points) whereas the Integrated Algebra had only 30% of the points (26/86) as non-multiple choice.
Too often students leave these questions blank which yields, um, zero points.
So it is super important for students to answer as many of these questions as they can and have knowledge on how the grading is done.
Click for Model Response Set that shows “student work” for graders to have examples of what work looks like at different point levels. For example, a 2 point question will have model responses that show 0, 1 and 2 points.
The Rating Guide has a broader rubric on how many points to award student work but this is often just a description so graders use both documents in the grading process.
Functions will not always be linear or exponential but in this question there is 1 linear and 3 exponential answer choices:
An exponential function has the variable on the exponent. A student in a classroom last year called it the “floating midget x”!
Let’s look at our options:
(1) compounded interest: exponential!! Notice the formula has A = P (1+r)^t — that exponent makes it exponential and not linear!!
(2) doubling…hey that’s Moore’s Law: exponential function that makes the phone/computer you are reading this on exist!!
(3) cell phone service we could write the equation like this: y = .20x + base looks mighty like y = mx + b
(4) decay function is exponential as it also uses an exponent
The maximum of the above graph f(x) is 5 (when x = 1, y = 5)>
Let’s put g(x) into the TI-84:
Look at the graph below: definitely goes higher than the original graph and therefore has a larger maximum value.
Check out the table below — maximum y value is 11 which definitely beats 5!
Math Confidence by Robin the Math Lady 